Surface-treated fillers for polyester films

ABSTRACT

A mono or multi-layer polyester film is described. Also described, is a process for producing the mono or multi-layer polyester film, the use of a surface-treated filler material product as a voiding agent in the mono or multi-layer polyester film, and an article including the mono or multi-layer polyester film. Further, use of the mono or multi-layer polyester film is described in packaging products, insulating materials, solar, marine or aviation applications, science, electronic or acoustic applications, wires, cables, radio frequency identifications, flexible circuits, graphic arts, stone paper, holograms, filter products, cosmetic products, household products, imaging, recording media, or industrial products.

The present invention relates to a mono or multi-layer polyester film, aprocess for producing the mono or multi-layer polyester film, the use ofa surface-treated filler material product as voiding agent in the monoor multi-layer polyester film, an article comprising the mono ormulti-layer polyester film as well as the use of the mono or multi-layerpolyester film in packaging products, insulating materials, solar,marine or aviation applications, science, electronic or acousticapplications, wires, cables, radio frequency identifications, flexiblecircuits, graphic arts, stone paper, holograms, filter products,cosmetic products, household products imaging, recording media, orindustrial products.

Polyester films such as cast films, blown films, double bubble films,mono axially and biaxially oriented polyester films are used in a greatvariety of applications, especially in packaging products, insulatingmaterials, solar, marine or aviation applications, science, electronicor acoustic applications, wires, cables, radio frequencyidentifications, flexible circuits, graphic arts, stone paper,holograms, filter products, cosmetic products, household productsimaging, recording media, or industrial products.

It is well known that oriented polyester films can be produced throughthe addition of foaming agents (chemical or gas) or voiding agents. Forexample, shaped article may be microvoided throughout the film byblending in voiding agents, i.e., small amounts of particles orincompatible polymers which form voids on stretching. This process iscalled “voiding” and may also be referred to as “cavitating” or“microvoiding”. Voids are typically obtained by incorporating about 5 toabout 50 wt.-% of small organic or inorganic particles or “inclusions”(referred in the art as “voiding” or “cavitation” agents) into a matrixpolymer and orienting the polymer by stretching in at least onedirection. During stretching, small cavities or “microvoids” are formedaround the voiding agent. When voids are introduced into polymer films,the resulting voided film not only has a lower density than thenon-voided film, but also becomes opaque and develops a paper-likesurface. This surface also has the advantage of increased printability;that is, the surface is capable of accepting many inks with asubstantially greater capacity over a non-voided film. In either case,the creation of small voids/holes in the article leads to a lowering ofthe density, an increase in the opacity and insulating properties, andinherent UV blocking without the need of a separate UV absorber becauseof the scattering of light by the voids. Microvoided articles have theadded benefit of lower overall film cost and greater easeseparation/recyclability, especially where such articles are used inpackaging applications such as, for example, as labels (see e.g. U.S.Pat. No. 7,297,755 B2).

In principle, the formation of voids is based on the generation ofmicrocracks at the interface between the polymer and the voiding agentduring film preparation, especially the longitudinal stretching. Duringsubsequent transverse stretching, these fine longitudinal cracks tearopen to form air-filled, closed hollow spaces. Hence, it seems plausiblethat the generation of voids during simultaneous orientation isdisproportionately more difficult than during sequential orientation.Indeed, it becomes apparent in practice that the particles incompatiblein polypropylene that are common, such as CaCO₃ or PBT, do not generatevoids at all or generate them only with a selective particle shape orparticle size (see e.g. WO03/033574) during simultaneous orientation.For this process, an alternative technology for generating voids bymeans of foaming agents was therefore developed.

It is appreciated that voided polyester films typically comprise a blendof polyester polymers and a voiding agent (organic material or inorganicfillers such as calcium carbonate) and are produced by forming a filmfrom said blend by casting or blowing with subsequent stretching ordrawing of the film in two orthogonal directions, at two differenttemperatures.

In the art, several attempts have been made to improve the mechanicaland optical properties of polyester films by adding inorganic fillermaterials and especially calcium carbonate-comprising filler materials.For instance, EP 0 554 654 A1 refers to a polyester resin film, which isbiaxially oriented, and, again, oriented in a machine direction, and hasa coating layer formed on at least one surface of the film, in which thecoating layer contains at least 50% by weight of a water-soluble orwater-dispersible polyester resin having a glass transition temperatureof at least 20° C. To prevent the adhesion of the coating layer to theheating roll during restretching, the coating layer may containinorganic or organic particles. Such particles are described as actingto improve the anti-blocking or slipping properties.

Likewise, DE 43 13 510 A1 relates to an oriented, mono or multilayerfilm having an overall thickness of ≤4 μm and a roughness on at leastone film surface of Ra<30 nm, where the surface gas-flow resistance onat least one film surface is t≤ad^(b) [s], where a=0 to 10 000 [s/μm],b=3.0 to 0, and d (overall film thickness)≤4 μm. The film may containfirst (I) and second (II) particles. The first particles aremonodisperse and have an aspect ratio of 1.0-1.2.

EP 1 052 269 A1 refers to a biaxially-oriented film with a thickness of1-500 μm and with a crystallizable thermoplastic as main component andfurther containing UV stabilizer(s) and white pigment(s).

EP 1 612 237 A1 refers to a thermoplastic biaxially oriented filmcontaining at least 500 ppm of pigment, at least 20 wt.-% of recycledmaterial of the same type is added. The film can be mono or multi-layerand is preferably 10 to 300 μm thick.

K. Nevalainen et al., “Voiding behaviour and microstructure of a filledpolyester film”; Materials Chemistry and Physics 92 (2005) 540-547refers to the voiding behaviour of a filled polyester film frompolyethylene terephthalate. The utilized filler was barium sulfate whichhad an average particle size between 1 and 2 μm.

K. Nevalainen et al., “The microstructure of polyethylene terephthalatematrix near to a void under uniaxial draw”; Materials Chemistry andPhysics 101 (2007) 103-111 describes the characterization of the matriximmediately adjacent to a void. In particular, it is referred to anuniaxial drawn PET film and the void formed around a spherical 5μm-sized glass bead filler.

A. Sudár et al., “The mechanism and kinetics of void formation andgrowth in particulate filled PE composites”; Polymer letters, Vol. 1,No. 11 (2007), 763-772 describes that the formation of voids in PEespecially depends on the nature of the matrix, i.e. in soft matricesthe number of voids is smaller and their size is larger at the samedeformation and filler content than in polymers with larger inherentmodulus.

However, the described films have the disadvantage that suitable voidsduring the preparation of the polyester films to create microporousfilms having low density and high opacity can be hardly prepared withoutfilm breakage.

One solution to the foregoing is disclosed in international patentapplication PCT/EP2016/078466 referring to a mono or multi-layerbiaxially oriented polyester film, wherein at least one layer of thefilm comprises at least one polyester in an amount ranging from 70 to99.9 wt.-% and a surface-treated filler material product in an amountranging from 0.1 to 30 wt.-%, based on the total weight of the layer,wherein the surface-treated filler material product comprises A) atleast one ground calcium carbonate-comprising filler material having aweight median particle size d₅₀ in the range from 0.5 μm to 2.5 μm, andB) a treatment layer on the surface of the at least one ground calciumcarbonate-comprising filler material comprising i. a phosphoric acidester blend of one or more phosphoric acid mono-ester and salty reactionproducts thereof and/or one or more phosphoric acid di-ester and saltyreaction products thereof, and/or ii. at least one saturated aliphaticlinear or branched carboxylic acid and salty reaction products thereof,and/or iii. at least one aliphatic aldehyde and/or salty reactionproducts thereof, and/or iv. at least one mono-substituted succinicanhydride consisting of succinic anhydride mono-substituted with a groupselected from a linear, branched, aliphatic and cyclic group having atotal amount of carbon atoms from at least C₂ to C₃₀ in the substituentand/or salty reaction products thereof, and/or v. at least onepolydialkylsiloxane, and/or vi. mixtures of the materials according toi. to v., wherein the surface-treated filler material product comprisesthe treatment layer in an amount of from 0.1 to 2.3 wt.-%, based on thetotal dry weight of the at least one ground calcium carbonate-comprisingfiller material

However, international patent application PCT/EP2016/078466 isabsolutely silent on polyester films having a high filler content,i.e. >30 wt.-%.

Thus, the provision of polyester films having a microporous structure athigh filler content, low density and high opacity remains of interest tothe skilled man. Furthermore, it is desired to keep the mechanical andoptical properties on a high level and to provide environmentallyfriendly films, which on the one hand are produced from raw materialsthat grow back and/or from recycled material, and on the other hand canbe disposed in an environmentally friendly manner.

Accordingly, it is an object of the present invention to provide apolyester film having a microporous structure. It would also bedesirable to provide a polyester film or corresponding layer, having amicroporous structure at high filler content. It would also be desirableto provide a polyester film or corresponding layer, having a microporousstructure at low density, especially a density being below the densitytypically achieved for corresponding films or layers using bariumsulfate or titanium dioxide as voiding agents. It would also bedesirable to provide a polyester film or layer having an opaqueappearance. It would be also desirable to provide a polyester film orlayer which can be prepared without film/layer breakage. It would bealso desirable to provide a polyester film or layer having goodmechanical and optical properties. It would be also desirable to providea polyester film or layer being environmentally friendly, which on theone hand is produced from raw materials that grow back and/or fromrecycled material and on the other hand can be disposed in anenvironmentally friendly manner.

Another object of the present invention is the provision of an inorganicvoiding agent for polyester films or layers. It would also be desirableto provide an inorganic voiding agent for polyester films or layers,which shows good dispersing properties and compounding performance inpolyester film/layer applications. It would also be desirable to providean inorganic voiding agent for polyester films or layers, which impartslow density to the film or layer. It would be also desirable to providean inorganic voiding agent which does not lead to film/layer breakagewhen preparing the polyester film or layer. It would also be desirableto provide an inorganic voiding agent for polyester films or layers,which allows a high filler content. It would also be desirable toprovide an inorganic voiding agent for polyester films or layers, whichimparts good mechanical properties such as tensile strength, elongationat break or modulus of elasticity. It would also be desirable to providean inorganic voiding agent for polyester films or layers which impartsan opaque appearance to the film or layer.

The foregoing objects and other objects are solved by the subject-matteras defined herein in the independent claims.

According to one aspect of the present invention, a mono or multi-layerpolyester film is provided. The mono or multi-layer polyester filmcomprises at least one layer comprising at least one polyester in anamount ranging from 20.0 to <70 wt.-% and a surface-treated fillermaterial product in an amount ranging from >30 to 80.0 wt.-%, based onthe total weight of the layer, wherein the surface-treated fillermaterial product comprises

-   -   A) at least one ground calcium carbonate-comprising filler        material having a weight median particle size d₅₀ in the range        from 0.5 μm to 3.0 μm, and    -   B) a treatment layer on the surface of the at least one ground        calcium carbonate-comprising filler material comprising        -   i. a phosphoric acid ester blend of one or more phosphoric            acid mono-ester and salty reaction products thereof and/or            one or more phosphoric acid di-ester and salty reaction            products thereof, and/or        -   ii. at least one saturated aliphatic linear or branched            carboxylic acid and salty reaction products thereof, and/or        -   iii. at least one aliphatic aldehyde and/or salty reaction            products thereof, and/or        -   iv. at least one mono-substituted succinic anhydride            consisting of succinic anhydride mono-substituted with a            group selected from a linear, branched, aliphatic and cyclic            group having a total amount of carbon atoms from at least C₂            to C₃₀ in the substituent and/or salty reaction products            thereof, and/or        -   v. at least one polydialkylsiloxane, and/or        -   vi. mixtures of the materials according to i. to v.,            wherein the surface-treated filler material product            comprises the treatment layer in an amount of from 0.1 to            2.3 wt.-%, based on the total dry weight of the at least one            ground calcium carbonate-comprising filler material.

According to a further aspect, a process for producing a mono ormulti-layer polyester film, as defined herein, is provided comprisingthe steps of:

-   -   a) providing a composition comprising at least one polyester and        a surface-treated filler material product, and    -   b) forming a film from the composition of step a), and wherein        the surface-treated filler material product comprises    -   A) at least one ground calcium carbonate-comprising filler        material having a weight median particle size d₅₀ in the range        from 0.5 μm to 3.0 μm, and    -   B) a treatment layer on the surface of the at least one ground        calcium carbonate-comprising filler material comprising        -   i. a phosphoric acid ester blend of one or more phosphoric            acid mono-ester and salty reaction products thereof and/or            one or more phosphoric acid di-ester and salty reaction            products thereof, and/or        -   ii. at least one saturated aliphatic linear or branched            carboxylic acid and salty reaction products thereof,            and/or iii. at least one aliphatic aldehyde and/or salty            reaction products thereof, and/or        -   iv. at least one mono-substituted succinic anhydride            consisting of succinic anhydride mono-substituted with a            group selected from a linear, branched, aliphatic and cyclic            group having a total amount of carbon atoms from at least C₂            to C₃₀ in the substituent and/or salty reaction products            thereof, and/or        -   v. at least one polydialkylsiloxane, and/or        -   vi. mixtures of the materials according to i. to v.,            wherein the surface-treated filler material product            comprises the treatment layer in an amount of from 0.1 to            2.3 wt.-%, based on the total dry weight of the at least one            ground calcium carbonate-comprising filler material.

According to still another aspect of the present invention, a use of asurface-treated filler material product as voiding agent in a mono ormulti-layer polyester film, as defined herein, is provided, wherein thesurface-treated filler material product comprises

-   -   A) at least one ground calcium carbonate-comprising filler        material having a weight median particle size d₅₀ in the range        from 0.5 μm to 3.0 μm, and    -   B) a treatment layer on the surface of the at least one ground        calcium carbonate-comprising filler material comprising        -   i. a phosphoric acid ester blend of one or more phosphoric            acid mono-ester and salty reaction products thereof and/or            one or more phosphoric acid di-ester and salty reaction            products thereof, and/or        -   ii. at least one saturated aliphatic linear or branched            carboxylic acid and salty reaction products thereof, and/or        -   iii. at least one aliphatic aldehyde and/or salty reaction            products thereof, and/or        -   iv. at least one mono-substituted succinic anhydride            consisting of succinic anhydride mono-substituted with a            group selected from a linear, branched, aliphatic and cyclic            group having a total amount of carbon atoms from at least C₂            to C₃₀ in the substituent and/or salty reaction products            thereof, and/or        -   v. at least one polydialkylsiloxane, and/or        -   vi. mixtures of the materials according to i. to v.,            wherein the surface-treated filler material product            comprises the treatment layer in an amount of from 0.1 to            2.3 wt.-%, based on the total dry weight of the at least one            ground calcium carbonate-comprising filler material.

According to still another aspect of the present invention, an articlecomprising a mono or multi-layer polyester film, as defined herein, isprovided, wherein the article is selected from the group consisting ofpackaging products, preferably flexible packaging products, food contactapplications, paper or glass coverings, insulating materials, solar,preferably photovoltaic front or backsheets, marine or aviationapplications, science, electronic or acoustic applications, preferablydisplays, wires, cables, radio frequency identifications, flexiblecircuits, graphic arts, preferably labels, stone paper, preferably bags,packages, boxes, books, booklets, brochures, loyalty cards, businesscards, greeting cards, corrugated boards, envelopes, food trays,labelling, games, tags, magazines, signage, billboards, stationary,diaries, pads or notebooks, and holograms, filter products, cosmeticproducts, household products imaging, recording media, preferablyphotographic paper, X-ray film or thermal transfer imaging or industrialproducts, preferably capacitors, release sheets, fiberglass panels,laminating films, hot stamping foils or insulation facing.

According to still another aspect of the present invention, a use of amono or multi-layer polyester film, as defined herein, in packagingproducts, preferably flexible packaging products, food contactapplications, paper or glass coverings, insulating materials, solar,preferably photovoltaic front or backsheets, marine or aviationapplications, science, electronic or acoustic applications, preferablydisplays, wires, cables, radio frequency identifications, flexiblecircuits, graphic arts, preferably labels, stone paper, preferably bags,packages, boxes, books, booklets, brochures, loyalty cards, businesscards, greeting cards, corrugated boards, envelopes, food trays,labelling, games, tags, magazines, signage, billboards, stationary,diaries, pads or notebooks, and holograms, filter products, cosmeticproducts, household products imaging, recording media, preferablyphotographic paper, X-ray film or thermal transfer imaging or industrialproducts, preferably capacitors, release sheets, fiberglass panels,laminating films, hot stamping foils or insulation facing is provided.

Advantageous embodiments of the present invention are defined herein andalso in the corresponding sub-claims.

According to one embodiment of the present invention, the at least onepolyester and surface-treated filler material product comprising layerof the film comprises the surface-treated filler material product in anamount ranging from 30.01 to 80.0 wt.-%, based on the total weight ofthe layer, preferably from 30.1 to 78.0 wt.-%, more preferably from 30.5to 75.0 wt.-%, even more preferably from 31.0 to 73.0 wt.-%, and mostpreferably from 35.0 to 70.0 wt.-%.

According to another embodiment the at least one polyester is selectedfrom the group consisting of polyglycolic acid (PGA), polylactic acid(PLA), polycaprolactone (PCL), polyhydroxybutyrate (PHB), polyethyleneterephthalate (PET), polybutylene terephthalate (PBT), polytrimethyleneterephthalate (PTT), polyethylene naphthalate (PEN), polyethylenefuranoate (PEF), bio-based polyesters, polyester-recycling materials andmixtures thereof.

According to yet another embodiment the at least one polyester andsurface-treated filler material product comprising layer of the filmcomprises the at least one polyester in an amount ranging from 20.0 to69.99 wt.-%, more preferably from 22.0 to 69.9 wt.-%, based on the totalweight of the layer.

According to one embodiment the at least one ground calciumcarbonate-comprising filler material is a wet or dry ground calciumcarbonate-comprising filler material and preferably is a wet groundcalcium carbonate-comprising filler. It is specifically contemplated orpreferred to use wet ground calcium-carbonate-comprising fillermaterials in relation to the foregoing aspects of the present invention.

According to another embodiment the at least one ground calciumcarbonate-comprising filler material is natural ground calciumcarbonate, precipitated calcium carbonate, modified calcium carbonate,surface-treated calcium carbonate, or a mixture thereof, and preferablynatural ground calcium carbonate.

According to yet another embodiment the at least one ground calciumcarbonate-comprising filler material has a) a weight median particlesize d₅₀ from 0.5 μm to 2.5 μm, preferably from 0.5 μm to 2.0 μm, evenmore preferably from 0.5 μm to 1.8 μm, and most preferably from 0.6 μmto 1.8 μm, and/or b) a top cut particle size d₉₈ of ≤15 μm preferably of≤10 μm, more preferably of ≤7.5 μm, even more preferably of ≤7 μm andmost preferably of ≤6.5 μm, and/or c) a fineness such that at least 15wt.-%, preferably at least 20 wt.-%, even more preferably at least 25wt.-% and most preferably from 30 to 40 wt.-% of all particles have aparticle size of <0.5 μm, and/or d) a specific surface area (BET) offrom 0.5 to 150 m²/g, preferably of from 0.5 to 50 m²/g, more preferablyof from 0.5 to 35 m²/g, and most preferably of from 0.5 to 15 m²/g, asmeasured using nitrogen and the BET method according to ISO 9277.

According to one embodiment the treatment layer on the surface of the atleast one ground calcium carbonate-comprising filler material comprisesat least one saturated aliphatic linear or branched carboxylic acid andsalty reaction products thereof, preferably the at least one saturatedaliphatic linear or branched carboxylic acid is selected from the groupconsisting of carboxylic acids consisting of pentanoic acid, hexanoicacid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid,undecanoic acid, lauric acid, tridecanoic acid, myristic acid,pentadecanoic acid, palmitic acid, heptadecanoic acid, stearic acid,nonadecanoic acid, arachidic acid, heneicosylic acid, behenic acid,tricosylic acid, lignoceric acid and mixtures thereof, and/or at leastone mono-substituted succinic anhydride consisting of succinic anhydridemono-substituted with a group selected from a linear, branched,aliphatic and cyclic group having a total amount of carbon atoms from atleast C₂ to C₃₀ in the substituent and/or salty reaction productsthereof.

According to another embodiment the surface-treated filler materialproduct comprises the treatment layer in an amount of from 0.2 to 2.0wt.-%, preferably from 0.4 to 1.9 wt.-% and most preferably from 0.5 to1.8 wt.-%, based on the total dry weight of the at least one groundcalcium carbonate-comprising filler material.

According to yet another embodiment the at least one polyester andsurface-treated filler material product comprising layer of the filmfurther comprises a thermoplastic polymer, preferably crosslinked with acrosslinking agent, the thermoplastic polymer is selected from the groupconsisting of a polyolefin, preferably selected from the groupconsisting of polypropylene, polyethylene, polybutylene, and mixturesthereof, a cyclic olefin copolymer (COC), a polyketone, a polysulphone,a fluoropolymer, a polyacetal, an ionomer, an acrylic resin, apolystyrene resin, a polyurethane, a polyamide, a polycarbonate, apolyacrylonitrile and a copolymerized resin and mixtures thereof, whichis dispersed in the at least one polyester.

According to one embodiment the at least one polyester andsurface-treated filler material product comprising layer of the filmcomprises the thermoplastic polymer in an amount ranging from 0.1 to29.9 wt.-%, preferably from 1 to 28 wt.-%, more preferably from 2 to 26wt.-%, even more preferably from 3 to 25 wt.-%, still more preferablyfrom 4.5 to 23 wt.-%, and most preferably from 4 to 20 wt.-%, based onthe total weight of the layer.

According to another embodiment the film, preferably the at least onelayer comprising the surface-treated filler material product, has a) adensity in the range from 1.8 to 2.4 g/cm³, preferably from 1.8 to 2.35g/cm³, more preferably from 1.85 to 2.3 g/cm³ and most preferably from1.9 to 2.25 g/m², and/or b) an opacity of ≥50%, preferably of ≥55% andmost preferably of ≥60%.

According to yet another embodiment the at least one polyester andsurface-treated filler material product comprising layer of the filmfurther comprises an inorganic filler material different from thesurface-treated filler material product and preferably selected from thegroup consisting of alumina, silica, titanium dioxide, alkaline metalsalts, such as barium carbonate, calcium sulfate, barium sulfate andmixtures thereof, preferably in an amount of 1 to 10 wt.-% based on thetotal weight of the layer.

According to one embodiment the film, preferably the at least onepolyester and surface-treated filler material product comprising layer,comprises an additive selected from the group consisting of lightstabilizers, preferably 2-hydroxybenzophenones, 2-hydroxybenzotriazoles,organonickel compounds, salicylic esters, cinnamic ester derivatives,resorcinol monobenzoates, oxanilides, hydroxybenzoic esters, stericallyhindered amines and triazines, more preferably the2-hydroxybenzotriazoles and triazines, most preferablyhydroxy-phenyl-triazin, optical brightener, blue dyes, preferably bluedyes soluble in polyester, antiblocking agents, white pigments andmixtures thereof.

According to another embodiment the film is a cast film, blown film, adouble bubble film or a mono axially oriented polyester film.

According to one embodiment the composition provided in step a) of theinventive process is a masterbatch obtained by mixing and/or kneadingthe at least one polyester and the surface-treated filler materialproduct to form a mixture and continuously pelletizing the obtainedmixture or a compound obtained by mixing and/or kneading the at leastone polyester and the surface-treated filler material product to form amixture and continuously pelletizing the obtained mixture.

According to another embodiment of the process, the composition providedin step a) is a masterbatch or compound comprising the surface-treatedfiller material product in an amount of from >30 to 85 wt.-%, preferablyfrom 35 to 80 wt.-% and more preferably from 40 to 70 wt.-%, based onthe total weight of the masterbatch or compound.

According to still another embodiment of the process the compositioncomprising at least one polyester and a surface-treated filler materialproduct of step a) is obtained by adding the surface-treated fillermaterial product, preferably before or after, to the polycondensationprocess of the at least one polyester.

According to one embodiment of the process, process steps a) and b) arecarried out simultaneously, preferably in that the at least onepolyester and the surface-treated filler material product are addeddirectly into an extruder to carry out step b).

According to another embodiment of the process, the process furthercomprises a step c) of stretching the film obtained in step b) in onlyone direction among machine direction (MD) or transverse direction (TD).

The at least one polyester and the surface-treated filler materialproduct, and, if present, other optional additives, may be mixed by theuse of a suitable mixer, e.g. a Henschel mixer, a super mixer, a tumblertype mixer or the like. According to another embodiment, process stepsa) and b) are carried out simultaneously, preferably in that the atleast one polyester and the surface-treated filler material product areadded directly into an extruder to carry out step b). According to yetanother embodiment, the composition comprising at least one polyesterand a surface-treated filler material product of step a) is obtained byadding the surface-treated filler material product, preferably before orafter, to the polycondensation process of the at least one polyester.

It should be understood that for the purposes of the present invention,the following terms have the following meanings:

The cast film process involves the extrusion of the respective polymersmelted through a slot or flat die to form a thin, molten sheet or film.This film is “pinned” or “fixed” to the surface of a chill roll(typically water-cooled and chrome-plated) by a blast of air from an airknife or vacuum box. The film quenches immediately and then has itsedges slit prior to winding. Because of the fast quench capabilities, acast film generally has much better optics than a blown film and can beproduced at higher line speeds. However, it has the disadvantage ofhigher scrap due to edge-trim, and very little film orientation in thecross-direction.

The term “mono axially oriented” polyester film indicates that the filmis a mono axially oriented film, i.e. the film has been subjected to astretching process in machine direction (MD) or transverse direction(TD), preferably machine direction (MD), obtaining thereby a monoaxially oriented film.

A “film” in the meaning of the present invention is a sheet or layer ofmaterial having a median thickness which is small compared to its lengthand width. For example, the term “film” may refer to a sheet or layer ofmaterial having a median thickness of from 0.5 to 2 000 μm, preferablyfrom 4 to 1 500 μm, more preferably from 5 to 1 300 μm and mostpreferably from 6 to 1 000 μm, e.g. from 8 to 500 μm. The film is in theform of a mono or multi-layer film.

A “monolayer” film refers to a film consisting of one layer only. A“multi-layer” film refers to a film consisting of two or more layerssuch as two to ten layers, preferably three layers, which are adjacentto each other. If the multi-layer film is a three layer film, the filmmay have the film structure A-B-A or A-B-C. In the multi-layer film, thecore layer is preferably voided.

The term “ground calcium carbonate-comprising filler” in the gist of thepresent invention means a calcium carbonate-comprising filler which hasbeen manufactured by a process including at least one grinding step.“Ground calcium carbonate-comprising fillers may be “wet ground” or “dryground”, wherein a “wet ground calcium carbonate-comprising filler” inthe meaning of the present invention is a ground calcium carbonatecomprising filler which has been manufactured by a process including atleast one grinding step in aqueous suspension with a solids contentbetween 20 and 80 wt.-% and a “dry ground calcium carbonate-comprisingfiller” is a ground calcium carbonate comprising filler which has beenmanufactured by a process including at least one grinding step inaqueous suspension with a solids content of more than 80 and up to 100wt.-%.

The term “microporous film” or “microporous layer” in the meaning of thepresent invention refers to a polyester film or a corresponding layerthat allows the passage of gases and moisture vapor due to the presenceof micropores. The presence of “micropores” of a polyester film or layercan be measured by its water vapor transmission rate (WVTR), which isspecified in g/(m²·day). For example, a polymer film or layer may beconsidered as being “microporous” if it has a WVTR of below 100g/(m²·day). The WVTR may be determined with a Lyssy L80-5000 measuringdevice according to ASTM E398.

The term “low density” in the meaning of the present invention refers toa mono or multi-layer polyester film or a corresponding layer having adensity from 1.8 to 2.4 g/cm³, preferably from 1.8 to 2.35 g/cm³, morepreferably from 1.85 to 2.3 g/cm³ and most preferably from 1.9 to 2.25g/m².

For the purpose of the present invention, the term “calciumcarbonate-comprising filler material” refers to a material thatcomprises at least 80 wt.-% calcium carbonate, based on the total dryweight of the calcium carbonate-comprising filler material.

“Natural ground calcium carbonate” (GCC) in the meaning of the presentinvention is a calcium carbonate obtained from natural sources, such aslimestone, marble, dolomite or chalk, and processed through a wettreatment such as grinding, screening and/or fractionation, for exampleby a cyclone or classifier.

“Modified calcium carbonate” (MCC) in the meaning of the presentinvention may feature a natural ground or precipitated calcium carbonatewith an internal structure modification or a surface-reaction product,i.e. “surface-reacted calcium carbonate”.

A “surface-reacted calcium carbonate” is a material comprising calciumcarbonate and insoluble, preferably at least partially crystalline,calcium salts of anions of acids on the surface. Preferably, theinsoluble calcium salt extends from the surface of at least a part ofthe calcium carbonate. The calcium ions forming said at least partiallycrystalline calcium salt of said anion originate largely from thestarting calcium carbonate material. MCCs are described, for example, inUS 2012/0031576 A1, WO 2009/074492 A1, EP 2 264 109 A1, EP 2 070 991 A1,or EP 2 264 108 A1.

The term “surface-treated filler material product” in the meaning of thepresent invention refers to a calcium carbonate-comprising fillermaterial which has been contacted with a surface treatment agent such asto obtain a coating layer on at least a part of the surface of thecalcium carbonate-comprising filler material.

The term “dry” calcium carbonate-comprising filler material isunderstood to be a filler material having less than 0.3% by weight ofwater relative to the filler material weight. The % water (equal to“residual total moisture content”) is determined according to theCoulometric Karl Fischer measurement method, wherein the filler materialis heated to 220° C., and the water content released as vapor andisolated using a stream of nitrogen gas (at 100 ml/min) is determined ina Coulometric Karl Fischer unit.

The term “polymer composition” refers to a composite material comprisingat least one additive (e.g., at least one filler) and at least onepolyester material which may be used in the production of a polymerproduct.

The term “polymer masterbach” (= or “masterbatch”) or “polymer compound”(= or “compound”) in the meaning of the present application relates to acomposition with a relative high filler content, that means >30 wt.-%(based on the total weight of the composition). A “polymer masterbatch”or “polymer compound” may be added to an unfilled or lowly filledpolyester during processing in order to achieve higher filler contents.Accordingly, the term “polymer composition” (=“composition”) as usedherein comprises both, “polymer masterbatches” and “polymer compounds”.

The term “specific surface area” (in m²/g) of the mineral filler in themeaning of the present invention is determined using the BET method withnitrogen as adsorbing gas, which is well known to the skilled man (ISO9277:2010). The total surface area (in m²) of the mineral filler is thenobtained by multiplying the specific surface area by the mass (in g) ofthe mineral filler prior to treatment.

Throughout the present document, the “particle size” of a calciumcarbonate-comprising filler is described by its distribution of particlesizes. The value d_(x) represents the diameter relative to which x % byweight of the particles have diameters less than d_(x). This means thatthe d₂₀ value is the particle size at which 20 wt.-% of all particlesare smaller, and the d₉₈ value is the particle size at which 98 wt.-% ofall particles are smaller. The d₉₈ value is also designated as “topcut”. The d₅₀ value is thus the weight median particle size, i.e. 50wt.-% of all grains are smaller than this particle size. For the purposeof the present invention the particle size is specified as weight medianparticle size d₅₀ unless indicated otherwise. For determining the weightmedian particle size d₅₀ value or the top cut particle size d₉₈ value aSedigraph 5100 device from the company Micromeritics, USA, can be used.The method and the instrument are known to the skilled person and arecommonly used to determine grain size of fillers and pigments. Themeasurement is carried out in an aqueous solution of 0.1 wt.-% Na₄P₂O₇.The samples are dispersed using a high speed stirrer and supersonics.

For the purpose of the present invention, the “solids content” of aliquid composition is a measure of the amount of material remainingafter all the solvent or water has been evaporated.

A “suspension” or “slurry” in the meaning of the present inventioncomprises insoluble solids and water, and optionally further additives,and usually contains large amounts of solids and, thus, is more viscousand can be of higher density than the liquid from which it is formed.

A “treatment layer” in the gist of the present invention refers to alayer, preferably a mono layer of a surface treatment agent on thesurface of the at least one ground calcium carbonate-comprising fillermaterial. The “treatment layer” comprises as surface treatment agenti.e. i. a phosphoric acid ester blend of one or more phosphoric acidmono-ester and salty reaction products thereof and/or one or morephosphoric acid di-ester and salty reaction products thereof, and/or ii.at least one saturated aliphatic linear or branched carboxylic acid andsalty reaction products thereof, and/or iii. at least one aliphaticaldehyde and/or salty reaction products thereof, and/or iv. at least onemono-substituted succinic anhydride consisting of succinic anhydridemono-substituted with a group selected from a linear, branched,aliphatic and cyclic group having a total amount of carbon atoms from atleast C₂ to C₃₀ in the substituent and/or salty reaction productsthereof, and/or v. at least one polydialkylsiloxane, and/or vi. mixturesof the materials according to i. to v.

Where the term “comprising” is used in the present description andclaims, it does not exclude other non-specified elements of major orminor functional importance. For the purposes of the present invention,the term “consisting of” is considered to be a preferred embodiment ofthe term “comprising of”. If hereinafter a group is defined to compriseat least a certain number of embodiments, this is also to be understoodto disclose a group, which preferably consists only of theseembodiments.

Whenever the terms “including” or “having” are used, these terms aremeant to be equivalent to “comprising” as defined above.

Where an indefinite or definite article is used when referring to asingular noun, e.g. “a”, “an” or “the”, this includes a plural of thatnoun unless something else is specifically stated.

Terms like “obtainable” or “definable” and “obtained” or “defined” areused interchangeably. This e.g. means that, unless the context clearlydictates otherwise, the term “obtained” does not mean to indicate thate.g. an embodiment must be obtained by e.g. the sequence of stepsfollowing the term “obtained” even though such a limited understandingis always included by the terms “obtained” or “defined” as a preferredembodiment.

The inventive mono or multi-layer polyester film comprises at least onelayer comprising at least one polyester in an amount ranging from 20.0to <70 wt.-% and a surface-treated filler material product in an amountranging from >30 to 80.0 wt.-%, based on the total weight of the film.The surface-treated filler material product comprises (A) at least oneground calcium carbonate-comprising filler material having a weightmedian particle size d₅₀ in the range from 0.5 μm to 3.0 μm, and (B) atreatment layer on the surface of the at least one ground calciumcarbonate-comprising filler material comprising i. a phosphoric acidester blend of one or more phosphoric acid mono-ester and salty reactionproducts thereof and/or one or more phosphoric acid di-ester and saltyreaction products thereof, and/or ii. at least one saturated aliphaticlinear or branched carboxylic acid and salty reaction products thereof,and/or iii. at least one aliphatic aldehyde and/or salty reactionproducts thereof, and/or iv. at least one mono-substituted succinicanhydride consisting of succinic anhydride mono-substituted with a groupselected from a linear, branched, aliphatic and cyclic group having atotal amount of carbon atoms from at least C₂ to C₃₀ in the substituentand/or salty reaction products thereof, and/or v. at least onepolydialkylsiloxane, and/or vi. mixtures of the materials according toi. to v. The surface-treated filler material product comprises thetreatment layer in an amount of from 0.1 to 2.3 wt.-%, based on thetotal dry weight of the at least one ground calcium carbonate-comprisingfiller material.

In the following details and preferred embodiments of the inventiveproduct will be set out in more detail. It is to be understood thatthese technical details and embodiments also apply to the inventiveprocess for producing said mono or multi-layer polyester film and theinventive use of the mono or multi-layer polyester film and thesurface-treated filler material product.

Polyester

The mono or multi-layer polyester film of the present inventioncomprises at least one layer comprising at least one polyester. It isappreciated that the at least one polyester is not restricted to aspecific material as long as the polymer is suitable for the preparationof a mono or multi-layer polyester film, especially a cast film, blownfilm, a double bubble film or a mono axially oriented polyester film.The skilled person will select the polyester in accordance with thedesired application of the mono or multi-layer polyester film.

It is one requirement of the present invention that the at least onepolyester and the surface-treated filler material product are present inthe same layer. Thus, the surface-treated filler material product isdispersed in the at least one polyester.

Accordingly, a multi-layer polyester film comprises at least one layercomprising the at least one polyester and the surface-treated fillermaterial product. If the multi-layer polyester film comprises two ormore polyester and surface-treated filler material product comprisinglayers, it is appreciated that the two or more layers may be the same ordifferent, e.g. may differ in the amounts of the at least one polyesterand the surface-treated filler material product.

It is appreciated that the expression “at least one” polyester meansthat the polyester comprises, preferably consists of, one or more kindsof polyester(s).

Accordingly, it should be noted that the at least one polyester may beone kind of polyester. Alternatively, the at least one polyester may bea mixture of two or more kinds of polyesters. For example, the at leastone polyester may be a mixture of two or three kinds of polyesters, liketwo kinds of polyester.

In one embodiment of the present invention, the at least one polyestercomprises, preferably consists of, one kind of polyester.

In general, the term “polyester” means a polymer obtained by thecondensation polymerization, at least in part, of a diol and adicarboxylic acid. As the dicarboxylic acid, terephthalic acid,isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, adipicacid, or sebacic acid can be used. As the diol, ethylene glycol,trimethylene glycol, tetramethylene glycol, or cyclohexanedimethanol canbe used.

Additionally or alternatively, the at least one polyester may be apartially or fully biobased polyester, i.e. a polyester in which themonomers are derived from renewable biomass sources. Examples ofmonomers include those which can be produced by using bioderivedcompounds. For example, the monomers include but are not limited toethylene glycol (EG), furandicarboxylic acid (FDCA), polyethylenefuranoate (PEF), which can be produced by using fructose, and mixturesthereof. Further monomers which are suitable for preparing the biobasedpolyester are described in e.g. WO2014/100265 A1, which is thus herewithincorporated by reference.

Additionally or alternatively, the at least one polyester is a polyesterrecycling material, such as PET recycling material such as PET bottlescrap from the PET recycling stream.

Thus, the inventive polyester is preferably polyglycolic acid,polylactic acid, polycaprolactone, polyhydroxybutyrate (PHB),polyethylene terephthalate, polytrimethylene terephthalate, polybutyleneterephthalate, poly(1,4-cyclohexanedimethylene terephthalate),polyethylene naphthalene-2,6-dicarboxylate, polyethylenenaphthalene-1,5-dicarboxylate, polytrimethylene naphthalate,polyethylene naphthalate/bibenzoate, or another combination derived fromthe monomers mentioned above, or else a mixture of these polyesters. Forexample, polyesters that may be used are selected from the groupconsisting of polyglycolic acid (PGA), polylactic acid (PLA),polycaprolactone (PCL), polyhydroxybutyrate (PHB), polyethyleneterephthalate (PET), polybutylene terephthalate (PBT), polytrimethyleneterephthalate (PTT), polyethylene naphthalate (PEN), polyethylenefuranoate (PEF), bio-based polyesters, polyester recycling materials andmixtures thereof.

Preference is given to polyethylene terephthalate (PET) and polyethylenenaphthalate (PEN), polyethylene furanoate (PEF) and mixtures thereof.Most preferably, the at least one polyester is polyethyleneterephthalate (PET).

These polyesters may be either a homopolymer or copolymer. As acomponent to be copolymerized, a diol component such as diethyleneglycol, neopentyl glycol or polyalkylene glycol and a dicarboxylic acidsuch as adipic acid, sebacic acid, phthalic acid, isophthalic acid or2,6-naphthalenedicarboxylic acid can be used.

In a preferred embodiment, the polyester also contains at least 0.5wt.-%, preferably at least 1 wt.-% and more preferably at least 2 wt.-%based on the total weight of the polyester, of units originated from themonomer isophthalic acid by condensation with a diol.

The inventive polyester preferably has an intrinsic viscosity measuredaccording to ISO 1628-1 (at 135° C. in decalin) 0.5 to 1.4 dl/g, morepreferably from 0.65 to 1.0 dl/g and most preferably from 0.65 to 0.85dl/g. For example, the inventive polyester has an intrinsic viscositymeasured according to ISO 1628-1 (at 135° C. in decalin) 0.78 to 0.82dl/g.

In one embodiment, the polyester has a crystallization temperature(T_(a)) measured by differential scanning calorimetry (DSC) of at least120° C., preferably of at least 140° C., e.g. in the range from 140 to180° C.

Additionally or alternatively, the polyethylene terephthalate (PET)preferably comprises diethylene glycol in an amount of ≤3 wt.-%, morepreferably of ≤1.5 wt.-% and most preferably of ≤1.2 wt.-%, based on thetotal weight of the polyethylene terephthalate (PET).

It is appreciated that the at least one polyester is preferablyamorphous or crystalline polyester, for example crystalline polyethyleneterephthalate (PET).

The at least one polyester and surface-treated filler material productcomprising layer of the mono or multi-layer polyester film comprises theat least one polyester in an amount ranging from 20.0 to <70 wt.-%,based on the total weight of the layer.

According to one embodiment, the at least one polyester andsurface-treated filler material product comprising layer of the mono ormulti-layer polyester film comprises the at least one polyester in anamount ranging from 20.0 to 69.9 wt.-%, more preferably from 22.0 to69.9 wt.-%, even more preferably from 25.0 to 69.5 wt.-%, still morepreferably from 27.0 to 69.0 wt.-% and most preferably from 30.0 to 65.0wt.-%. based on the total weight of the layer.

In case the at least one layer of the mono or multi-layer polyester filmfurther comprises a thermoplastic polymer, the at least one polyesterand surface-treated filler material product comprising layer of the filmcomprises the at least one polyester in an amount ranging from 22.0 to69.9 wt.-%, preferably from 25.0 to 69.5 wt.-%, even more preferablyfrom 27.0 to 69.0 wt.-% and most preferably from 30.0 to 65.0 wt.-%,based on the total weight of the layer.

Surface-Treated Filler Material Product

The at least one layer of the mono or multi-layer polyester film of thepresent invention also comprises a surface-treated filler materialproduct, wherein the surface-treated filler material product comprisesat least one ground calcium carbonate-comprising filler material. Thesurface-treated filler material product has several essential features,which are defined in claim 1 and will be described in more detail in thefollowing.

The at least one ground calcium carbonate-comprising filler material isa wet or dry ground calcium carbonate-comprising filler material.Preferably, the at least one ground calcium carbonate-comprising fillermaterial is a wet ground calcium carbonate-comprising filler material.

In general, the grinding step can be carried out with any conventionalgrinding device, for example, under conditions such that refinementpredominantly results from impacts with a secondary body, i.e. in one ormore of: a ball mill, a rod mill, a vibrating mill, a roll crusher, acentrifugal impact mill, a vertical bead mill an attrition mill, a pinmill, a hammer mill, a pulverizer, a shredder, a de-clumper, a knifecutter, or other such equipment known to the skilled man.

In case the at least one ground calcium carbonate-comprising fillermaterial is a wet ground calcium carbonate-comprising filler material,the wet grinding step may be performed under conditions such thatautogenous grinding takes place and/or by horizontal ball milling,and/or other such processes known to the skilled man. The processedground calcium carbonate-comprising filler material thus obtained may bewashed and dewatered by well-known processes, e.g. by flocculation,filtration or forced evaporation prior to drying. The subsequent step ofdrying may be carried out in a single step such as spray drying, or inat least two steps, e.g. by applying a first heating step to the wetground calcium carbonate-comprising filler material in order to reducethe associated moisture content to a level which is not greater thanabout 0.5 wt.-%, based on the total dry weight of the at least one wetground calcium carbonate-comprising filler material. The residual totalmoisture content of the filler can be measured by the Karl FischerCoulometric titration method, desorbing the moisture in an oven at 195°C. and passing it continuously into the KF Coulometer (Mettler ToledoCoulometric KF Titrator C30, combined with Mettler oven DO 0337) usingdry N₂ at 100 ml/min for 10 min. The residual total moisture content canbe determined with a calibration curve and also a blind of 10 min gasflow without a sample can be taken into account. The residual totalmoisture content may be further reduced by applying a second heatingstep to the at least one wet ground calcium carbonate-comprising fillermaterial. In case said drying is carried out by more than one dryingsteps, the first step may be carried out by heating in a hot current ofair, while the second and further drying steps are preferably carriedout by an indirect heating in which the atmosphere in the correspondingvessel comprises a surface treatment agent. It is also common that theat least one wet ground calcium carbonate-comprising filler material issubjected to a beneficiation step (such as a flotation, bleaching ormagnetic separation step) to remove impurities.

In another preferred embodiment, the at least one ground calciumcarbonate-comprising filler material is a material being ground in ahorizontal ball mill, and subsequently dried by using the well-knownprocess of spray drying.

The at least one ground calcium carbonate-comprising filler material inthe meaning of the present invention refers to a filler materialselected from among natural ground calcium carbonate (GCC), precipitatedcalcium carbonate (PCC), modified calcium carbonate (MCC),surface-treated calcium carbonate, or mixtures thereof.

According to a preferred embodiment, the at least one ground calciumcarbonate-comprising filler material is a natural ground calciumcarbonate (GCC), more preferably the ground calcium carbonate-carbonatecomprising filler is a wet ground natural calcium carbonate.

GCC is understood to be a naturally occurring form of calcium carbonate,mined from sedimentary rocks such as limestone or chalk, or frommetamorphic marble rocks and processed through a treatment such asgrinding, screening and/or fractionizing in wet form, for example by acyclone or classifier. In one embodiment of the present invention, theGCC is selected from the group comprising marble, chalk, dolomite,limestone and mixtures thereof.

“Precipitated calcium carbonate” (PCC) in the meaning of the presentinvention is a synthesized material, generally obtained by precipitationfollowing reaction of carbon dioxide and lime in an aqueous environmentor by precipitation of a calcium and carbonate ion source in water or byprecipitation of calcium and carbonate ions, for example CaCl₂) andNa₂CO₃, out of solution. Further possible ways of producing PCC are thelime soda process, or the Solvay process in which PCC is a by-product ofammonia production. Precipitated calcium carbonate exists in threeprimary crystalline forms: calcite, aragonite and vaterite, and thereare many different polymorphs (crystal habits) for each of thesecrystalline forms. Calcite has a trigonal structure with typical crystalhabits such as scalenohedral (S-PCC), rhombohedral (R-PCC), hexagonalprismatic, pinacoidal, colloidal (C-PCC), cubic, and prismatic (P-PCC).Aragonite is an orthorhombic structure with typical crystal habits oftwinned hexagonal prismatic crystals, as well as a diverse assortment ofthin elongated prismatic, curved bladed, steep pyramidal, chisel shapedcrystals, branching tree, and coral or worm-like form. Vaterite belongsto the hexagonal crystal system. The obtained PCC slurry can bemechanically dewatered and dried.

A modified calcium carbonate may feature a GCC or PCC with an internalstructure modification or a surface-reacted GCC or PCC. Asurface-reacted calcium carbonate may be prepared by providing a GCC orPCC in form of an aqueous suspension, and adding an acid to saidsuspension. Suitable acids are, for example, sulfuric acid, hydrochloricacid, phosphoric acid, citric acid, oxalic acid, or a mixture thereof.In a next step, the calcium carbonate is treated with gaseous carbondioxide. If a strong acid such as sulfuric acid or hydrochloric acid isused for the acid treatment step, the carbon dioxide will formautomatically in situ. Alternatively or additionally, the carbon dioxidecan be supplied from an external source. Surface-reacted calciumcarbonates are described, for example, in US 2012/0031576 A1, WO2009/074492 A1, EP 2 264 109 A1, EP 2 070 991 A1, or EP 2 264 108 A1.

In one preferred embodiment, the at least one ground calciumcarbonate-comprising filler material is marble, more preferably a wetground marble.

It is appreciated that the amount of ground calcium carbonate in the atleast one calcium carbonate-comprising filler material is at least 80wt.-%, e.g. at least 95 wt.-%, preferably between 97 and 100 wt.-%, morepreferably between 98.5 and 99.95 wt.-%, based on the total dry weightof the at least one ground calcium carbonate-comprising filler material.

The at least one ground calcium carbonate-comprising filler material ispreferably in the form of a particulate material, and may have aparticle size distribution as conventionally employed for thematerial(s) involved in the type of product to be produced. In general,it is one specific requirement of the present invention that the atleast one ground calcium carbonate-comprising filler material has aweight median particle size d₅₀ value in the range from 0.5 to 3.0 μm.For example, the at least one ground calcium carbonate-comprising fillermaterial has a weight median particle size d₅₀ from 0.5 μm to 2 μm,preferably from 0.5 μm to 2 μm, even more preferably from 0.5 μm to 1.8μm, and most preferably from 0.6 μm to 1.8 μm, such as of about 0.8 μmor about 1.7 μm.

It is preferred that the at least one ground calciumcarbonate-comprising filler material has a top cut (d₉₈) of ≤15 μm. Forexample, the at least one ground calcium carbonate-comprising fillermaterial has a top cut (d₉₈) of ≤10 μm, preferably of ≤7.5 μm, morepreferably of ≤7 μm and most preferably of ≤6.5 μm.

It is appreciated that the weight median particle size d₅₀ value and thetop cut (d₉₈) of the at least one ground calcium carbonate-comprisingfiller material fulfil a specific ratio. For example, the at least oneground calcium carbonate-comprising filler material has a ratio ofweight median particle size d₅₀ value and the top cut (d₉₈) [d₅₀/d₉₈] offrom 0.1 to 0.4, preferably from 0.1 to 0.3 and most preferably from 0.2to 0.3.

Additionally or alternatively, the at least one ground calciumcarbonate-comprising filler material has a fineness such that at least15 wt.-%, preferably at least 20 wt.-%, even more preferably at least 25wt.-% and most preferably from 30 to 40 wt.-% of all particles have aparticle size of <0.5 μm.

In one embodiment, the at least one ground calcium carbonate-comprisingfiller material has

-   -   i) a weight median particle size d₅₀ from 0.5 to 3.0 μm,        preferably from 0.5 μm to 2 μm, more preferably from 0.5 μm to 2        μm, even more preferably from 0.5 μm to 1.8 μm, and most        preferably from 0.6 μm to 1.8 μm, and    -   ii) a top cut particle size d₉₈ of ≤15 μm preferably of ≤10 μm,        more preferably of ≤7.5 μm, even more preferably of ≤7 μm and        most preferably of ≤6.5 μm, and    -   iii) a fineness such that at least 15 wt.-%, preferably at least        20 wt.-%, even more preferably at least 25 wt.-% and most        preferably from 30 to 40 wt.-% of all particles have a particle        size of <0.5 μm.

For example, the at least one ground calcium carbonate-comprising fillermaterial has

-   -   i) a weight median particle size d₅₀ from 0.6 μm to 1.8 μm, and    -   ii) a top cut (d₉₈) of ≤6.5 μm, and    -   iii) a fineness such that 30 to 40 wt.-% of all particles have a        particle size of <0.5 μm.

It is further appreciated that the at least one ground calciumcarbonate-comprising filler material preferably has a BET specificsurface area of from 0.5 and 150 m²/g, as measured using nitrogen andthe BET method according to ISO 9277. For example, the at least oneground calcium carbonate-comprising filler material has a specificsurface area (BET) of from 0.5 to 50 m²/g, more preferably of from 0.5to 35 m²/g and most preferably of from 0.5 to 15 m²/g, as measured usingnitrogen and the BET method according to ISO 9277.

In one embodiment of the present invention, the at least one groundcalcium carbonate-comprising filler material is preferably a marblehaving a median particle size diameter d₅₀ value from 0.5 to 3.0 μm,preferably from 0.5 μm to 2 μm, more preferably from 0.5 μm to 2 μm,even more preferably from 0.5 μm to 1.8 μm, and most preferably from 0.6μm to 1.8 μm, such as of about 0.8 μm or about 1.7 μm. In this case, theat least one ground calcium carbonate-comprising filler materialexhibits a BET specific surface area of from 0.5 to 150 m²/g, preferablyof from 0.5 to 50 m²/g, more preferably of from 0.5 to 35 m²/g and mostpreferably of from 0.5 to 15 m²/g, measured using nitrogen and the BETmethod according to ISO 9277.

According to the present invention the at least one ground calciumcarbonate-comprising filler material has a residual moisture content of≤1 wt.-%, based on the total dry weight of the at least one groundcalcium carbonate-comprising filler material. Depending on the at leastone ground calcium carbonate-comprising filler material, the at leastone ground calcium carbonate-comprising filler material has a residualtotal moisture content of from 0.01 to 1 wt.-%, preferably from 0.01 to0.2 wt.-%, more preferably from 0.02 to 0.15 wt.-% and most preferablyfrom 0.04 to 0.15 wt.-%, based on the total dry weight of the at leastone ground calcium carbonate-comprising filler material.

For example, in case a ground and spray dried marble is used as the atleast one ground calcium carbonate-comprising filler material, theresidual total moisture content of the at least one ground calciumcarbonate-comprising filler material is preferably of from 0.01 to 0.1wt.-%, more preferably from 0.02 to 0.08 wt.-% and most preferably from0.04 to 0.07 wt.-% based on the total dry weight of the at least oneground calcium carbonate-comprising filler material. If a PCC is used asthe at least one ground calcium carbonate-comprising filler material,the residual total moisture content of the at least one ground calciumcarbonate-comprising filler material is preferably of from 0.01 to 0.2wt.-%, more preferably from 0.05 to 0.17 wt.-% and most preferably from0.05 to 0.10 wt.-%, based on the total dry weight of the at least oneground calcium carbonate-comprising filler material.

According to the present invention the surface-treated filler materialproduct further comprises a treatment layer on the surface of the atleast one ground calcium carbonate-comprising filler material.

The treatment layer comprises

-   -   i. a phosphoric acid ester blend of one or more phosphoric acid        mono-ester and salty reaction products thereof and/or one or        more phosphoric acid di-ester and salty reaction products        thereof, and/or    -   ii. at least one saturated aliphatic linear or branched        carboxylic acid and salty reaction products thereof, and/or    -   iii. at least one aliphatic aldehyde and/or salty reaction        products thereof, and/or    -   iv. at least one mono-substituted succinic anhydride consisting        of succinic anhydride mono-substituted with a group selected        from a linear, branched, aliphatic and cyclic group having a        total amount of carbon atoms from at least C₂ to C₃₀ in the        substituent and/or salty reaction products thereof, and/or    -   v. at least one polydialkylsiloxane, and/or    -   vi. mixtures of the materials according to i. to v.

According to one embodiment of the present invention, thesurface-treated filler material product comprises a treatment layer onat least a part of the surface of the at least one ground calciumcarbonate-comprising filler material, wherein the treatment layercomprises a phosphoric acid ester blend of one or more phosphoric acidmono-ester and salty reaction products thereof and/or one or morephosphoric acid di-ester and salty reaction products thereof.

The term “phosphoric acid mono-ester” in the meaning of the presentinvention refers to an o-phosphoric acid molecule mono-esterified withone alcohol molecule selected from unsaturated or saturated, branched orlinear, aliphatic or aromatic alcohols having a total amount of carbonatoms from C6 to C30, preferably from C8 to C22, more preferably from C8to C20, and most preferably from C8 to C18 in the alcohol substituent.

The term “phosphoric acid di-ester” in the meaning of the presentinvention refers to an o-phosphoric acid molecule di-esterified with twoalcohol molecules selected from the same or different, unsaturated orsaturated, branched or linear, aliphatic or aromatic alcohols having atotal amount of carbon atoms from C6 to C30, preferably from C8 to C22,more preferably from C8 to C20, and most preferably from C8 to C18 inthe alcohol substituent.

The term “salty reaction products of a phosphoric acid ester blend ofone or more phosphoric acid mono-esters and/or one or more phosphoricacid di-esters” in the meaning of the present invention refers toproducts obtained by contacting a calcium carbonate-comprising fillermaterial with one or more phosphoric acid mono-ester and one or morephosphoric acid di-ester and optionally phosphoric acid. Said saltyreaction products are formed between the applied one or more phosphoricacid mono-ester and one or more phosphoric acid di-ester and optionallyphosphoric acid and reactive molecules located at the surface of thefiller material, preferably the at least one ground calciumcarbonate-comprising filler material.

Alkyl esters of phosphoric acid are well known in the industryespecially as surfactants, lubricants and antistatic agents (DieTenside; Kosswig and Stache, Carl Hanser Verlag Munchen, 1993).

The synthesis of alkyl esters of phosphoric acid by different methodsand the surface treatment of minerals with alkyl esters of phosphoricacid are well known by the skilled man, e.g. from Pesticide Formulationsand Application Systems: 15th Volume; Collins H M, Hall F R, HopkinsonM, STP1268; Published: 1996, U.S. Pat. Nos. 3,897,519 A, 4,921,990 A,4,350,645 A, 6,710,199 B2, 4,126,650 A, 5,554,781 A, EP 1092000 B1 andWO 2008/023076 A1.

It is appreciated that the expression “one or more” phosphoric acidmono-ester means that one or more kinds of phosphoric acid mono-estermay be present in the phosphoric acid ester blend.

Accordingly, it should be noted that the one or more phosphoric acidmono-ester may be one kind of phosphoric acid mono-ester. Alternatively,the one or more phosphoric acid mono-ester may be a mixture of two ormore kinds of phosphoric acid mono-ester. For example, the one or morephosphoric acid mono-ester may be a mixture of two or three kinds ofphosphoric acid mono-ester, like two kinds of phosphoric acidmono-ester.

In one embodiment of the present invention, the one or more phosphoricacid mono-ester consists of an o-phosphoric acid molecule esterifiedwith one alcohol selected from unsaturated or saturated, branched orlinear, aliphatic or aromatic alcohols having a total amount of carbonatoms from C6 to C30 in the alcohol substituent. For example, the one ormore phosphoric acid mono-ester consists of an o-phosphoric acidmolecule esterified with one alcohol selected from unsaturated orsaturated, branched or linear, aliphatic or aromatic alcohols having atotal amount of carbon atoms from C8 to C22, more preferably from C8 toC20 and most preferably from C8 to C18 in the alcohol substituent.

In one embodiment of the present invention, the one or more phosphoricacid mono-ester consists of an o-phosphoric acid molecule esterifiedwith one alcohol selected from saturated and linear or branched andaliphatic alcohols having a total amount of carbon atoms from C6 to C30in the alcohol substituent. For example, the one or more phosphoric acidmono-ester consists of an o-phosphoric acid molecule esterified with onealcohol selected from saturated and linear or branched and aliphaticalcohols having a total amount of carbon atoms from C8 to C22, morepreferably from C8 to C20 and most preferably from C8 to C18 in thealcohol substituent.

In one embodiment of the present invention, the one or more phosphoricacid mono-ester consists of an o-phosphoric acid molecule esterifiedwith one alcohol selected from saturated and linear and aliphaticalcohols having a total amount of carbon atoms from C6 to C30,preferably from C8 to C22, more preferably from C8 to C20 and mostpreferably from C8 to C18 in the alcohol substituent. Alternatively, theone or more phosphoric acid mono-ester consists of an o-phosphoric acidmolecule esterified with one alcohol selected from saturated andbranched and aliphatic alcohols having a total amount of carbon atomsfrom C6 to C30, preferably from C8 to C22, more preferably from C8 toC20 and most preferably from C8 to C18 in the alcohol substituent.

In one embodiment of the present invention, the one or more phosphoricacid mono-ester is selected from the group comprising hexyl phosphoricacid mono-ester, heptyl phosphoric acid mono-ester, octyl phosphoricacid mono-ester, 2-ethylhexyl phosphoric acid mono-ester, nonylphosphoric acid mono-ester, decyl phosphoric acid mono-ester, undecylphosphoric acid mono-ester, dodecyl phosphoric acid mono-ester,tetradecyl phosphoric acid mono-ester, hexadecyl phosphoric acidmono-ester, heptylnonyl phosphoric acid mono-ester, octadecyl phosphoricacid mono-ester, 2-octyl-1-decylphosphoric acid mono-ester,2-octyl-1-dodecylphosphoric acid mono-ester and mixtures thereof.

For example, the one or more phosphoric acid mono-ester is selected fromthe group comprising 2-ethylhexyl phosphoric acid mono-ester, hexadecylphosphoric acid mono-ester, heptylnonyl phosphoric acid mono-ester,octadecyl phosphoric acid mono-ester, 2-octyl-1-decylphosphoric acidmono-ester, 2-octyl-1-dodecylphosphoric acid mono-ester and mixturesthereof. In one embodiment of the present invention, the one or morephosphoric acid mono-ester is 2-octyl-1-dodecylphosphoric acidmono-ester.

It is appreciated that the expression “one or more” phosphoric aciddi-ester means that one or more kinds of phosphoric acid di-ester may bepresent in the treatment layer of the surface-treated material productand/or the phosphoric acid ester blend.

Accordingly, it should be noted that the one or more phosphoric aciddi-ester may be one kind of phosphoric acid di-ester. Alternatively, theone or more phosphoric acid di-ester may be a mixture of two or morekinds of phosphoric acid di-ester. For example, the one or morephosphoric acid di-ester may be a mixture of two or three kinds ofphosphoric acid di-ester, like two kinds of phosphoric acid di-ester.

In one embodiment of the present invention, the one or more phosphoricacid di-ester consists of an o-phosphoric acid molecule esterified withtwo alcohols selected from unsaturated or saturated, branched or linear,aliphatic or aromatic alcohols having a total amount of carbon atomsfrom C6 to C30 in the alcohol substituent. For example, the one or morephosphoric acid di-ester consists of an o-phosphoric acid moleculeesterified with two fatty alcohols selected from unsaturated orsaturated, branched or linear, aliphatic or aromatic alcohols having atotal amount of carbon atoms from C8 to C22, more preferably from C8 toC20 and most preferably from C8 to C18 in the alcohol substituent.

It is appreciated that the two alcohols used for esterifying thephosphoric acid may be independently selected from the same ordifferent, unsaturated or saturated, branched or linear, aliphatic oraromatic alcohols having a total amount of carbon atoms from C6 to C30in the alcohol substituent. In other words, the one or more phosphoricacid di-ester may comprise two substituents being derived from the samealcohols or the phosphoric acid di-ester molecule may comprise twosubstituents being derived from different alcohols.

In one embodiment of the present invention, the one or more phosphoricacid di-ester consists of an o-phosphoric acid molecule esterified withtwo alcohols selected from the same or different, saturated and linearor branched and aliphatic alcohols having a total amount of carbon atomsfrom C6 to C30 in the alcohol substituent. For example, the one or morephosphoric acid di-ester consists of an o-phosphoric acid moleculeesterified with two alcohols selected from the same or different,saturated and linear or branched and aliphatic alcohols having a totalamount of carbon atoms from C8 to C22, more preferably from C8 to C20and most preferably from C8 to C18 in the alcohol substituent.

In one embodiment of the present invention, the one or more phosphoricacid di-ester consists of an o-phosphoric acid molecule esterified withtwo alcohols selected from the same or different, saturated and linearand aliphatic alcohols having a total amount of carbon atoms from C6 toC30, preferably from C8 to C22, more preferably from C8 to C20 and mostpreferably from C8 to C18 in the alcohol substituent. Alternatively, theone or more phosphoric acid di-ester consists of an o-phosphoric acidmolecule esterified with two alcohols selected from the same ordifferent, saturated and branched and aliphatic alcohols having a totalamount of carbon atoms from C6 to C30, preferably from C8 to C22, morepreferably from C8 to C20 and most preferably from C8 to C18 in thealcohol substituent.

In one embodiment of the present invention, the one or more phosphoricacid di-ester is selected from the group comprising hexyl phosphoricacid di-ester, heptyl phosphoric acid di-ester, octyl phosphoric aciddi-ester, 2-ethylhexyl phosphoric acid di-ester, nonyl phosphoric aciddi-ester, decyl phosphoric acid di-ester, undecyl phosphoric aciddi-ester, dodecyl phosphoric acid di-ester, tetradecyl phosphoric aciddi-ester, hexadecyl phosphoric acid di-ester, heptylnonyl phosphoricacid di-ester, octadecyl phosphoric acid di-ester,2-octyl-1-decylphosphoric acid di-ester, 2-octyl-1-dodecylphosphoricacid di-ester and mixtures thereof.

For example, the one or more phosphoric acid di-ester is selected fromthe group comprising 2-ethylhexyl phosphoric acid di-ester, hexadecylphosphoric acid di-ester, heptylnonyl phosphoric acid di-ester,octadecyl phosphoric acid di-ester, 2-octyl-1-decylphosphoric aciddi-ester, 2-octyl-1-dodecylphosphoric acid di-ester and mixturesthereof. In one embodiment of the present invention, the one or morephosphoric acid di-ester is 2-octyl-1-dodecylphosphoric acid di-ester.

In one embodiment of the present invention, the one or more phosphoricacid mono-ester is selected from the group comprising 2-ethylhexylphosphoric acid mono-ester, hexadecyl phosphoric acid mono-ester,heptylnonyl phosphoric acid mono-ester, octadecyl phosphoric acidmono-ester, 2-octyl-1-decylphosphoric acid mono-ester,2-octyl-1-dodecylphosphoric acid mono-ester and mixtures thereof and theone or more phosphoric acid di-ester is selected from the groupcomprising 2-ethylhexyl phosphoric acid di-ester, hexadecyl phosphoricacid di-ester, heptylnonyl phosphoric acid di-ester, octadecylphosphoric acid di-ester, 2-octyl-1-decylphosphoric acid di-ester,2-octyl-1-dodecylphosphoric acid di-ester and mixtures thereof.

For example, at least a part of the surface of the calciumcarbonate-comprising filler material comprises a phosphoric acid esterblend of one phosphoric acid mono-ester and salty reaction productsthereof and one phosphoric acid di-ester and salty reaction productsthereof. In this case, the one phosphoric acid mono-ester is selectedfrom the group comprising 2-ethylhexyl phosphoric acid mono-ester,hexadecyl phosphoric acid mono-ester, heptylnonyl phosphoric acidmono-ester, octadecyl phosphoric acid mono-ester,2-octyl-1-decylphosphoric acid mono-ester and2-octyl-1-dodecylphosphoric acid mono-ester, the one phosphoric aciddi-ester is selected from the group comprising 2-ethylhexyl phosphoricacid di-ester, hexadecyl phosphoric acid di-ester, heptylnonylphosphoric acid di-ester, octadecyl phosphoric acid di-ester,2-octyl-1-decylphosphoric acid di-ester and 2-octyl-1-dodecylphosphoricacid di-ester.

If at least a part of the surface of the at least one ground calciumcarbonate-comprising filler material comprises a phosphoric acid esterblend of one phosphoric acid mono-ester and salty reaction productsthereof and one phosphoric acid di-ester and salty reaction productsthereof, it is appreciated that the alcohol substituent of the onephosphoric acid mono-ester and the one phosphoric acid di-ester arepreferably the same. For example, at least a part of the surface of theat least one ground calcium carbonate-comprising filler materialcomprises a phosphoric acid ester blend of 2-ethylhexyl phosphoric acidmono-ester and salty reaction products thereof and 2-ethylhexylphosphoric acid di-ester and salty reaction products thereof.

Alternatively, at least a part of the surface of the at least one groundcalcium carbonate-comprising filler material comprises a phosphoric acidester blend of 2-octyl-1-decyl phosphoric acid mono-ester and saltyreaction products thereof and 2-octyl-1-decyl phosphoric acid di-esterand salty reaction products thereof. Alternatively, at least a part ofthe surface of the at least one ground calcium carbonate-comprisingfiller material comprises a phosphoric acid ester blend of hexadecylphosphoric acid mono-ester and salty reaction products thereof andhexadecyl phosphoric acid di-ester and salty reaction products thereof.Alternatively, at least a part of the surface of the at least one groundcalcium carbonate-comprising filler material comprises a phosphoric acidester blend of octadecyl phosphoric acid mono-ester and salty reactionproducts thereof and octadecyl phosphoric acid di-ester and saltyreaction products thereof. Alternatively, at least a part of the surfaceof the at least one ground calcium carbonate-comprising filler materialcomprises a phosphoric acid ester blend of 2-octyl-1-dodecylphosphoricacid mono-ester and salty reaction products thereof and2-octyl-1-dodecylphosphoric acid di-ester and salty reaction productsthereof.

In one embodiment of the present invention, at least a part of thesurface of the at least one ground calcium carbonate-comprising fillermaterial comprises a phosphoric acid ester blend of two or morephosphoric acid mono-esters and salty reaction products thereof and twoor more phosphoric acid di-ester and salty reaction products thereof. Inthis case, the two or more phosphoric acid mono-esters are selected fromthe group comprising 2-ethylhexyl phosphoric acid mono-ester, hexadecylphosphoric acid mono-ester, heptylnonyl phosphoric acid mono-ester,octadecyl phosphoric acid mono-ester, 2-octyl-1-decyl phosphoric acidmono-ester and 2-octyl-1-dodecylphosphoric acid mono-ester, the two ormore phosphoric acid di-ester are selected from the group comprising2-ethylhexyl phosphoric acid di-ester, hexadecyl phosphoric aciddi-ester, heptylnonyl phosphoric acid di-ester, octadecyl phosphoricacid di-ester, 2-octyl-1-decyl phosphoric acid di-ester and2-octyl-1-dodecylphosphoric acid di-ester.

In one embodiment of the present invention, at least a part of thesurface of the at least one ground calcium carbonate-comprising fillermaterial comprises a phosphoric acid ester blend of two phosphoric acidmono-esters and salty reaction products thereof and two phosphoric aciddi-esters and salty reaction products thereof. For example, at least apart of the surface of the at least one ground calciumcarbonate-comprising filler material comprises a phosphoric acid esterblend of hexadecyl phosphoric acid mono-ester, octadecyl phosphoric acidmono-ester, hexadecyl phosphoric acid di-ester, octadecyl phosphoricacid di-ester and salty reaction products thereof and salty reactionproducts thereof.

According to one embodiment of the present invention, the phosphoricacid ester blend on at least a part of the surface of the at least oneground calcium carbonate-comprising filler material comprises the one ormore phosphoric acid mono-ester and salty reaction products thereof tothe one or more phosphoric acid di-ester and salty reaction productsthereof in a specific molar ratio. In particular, the molar ratio of theone or more phosphoric acid mono-ester and salty reaction productsthereof to the one or more phosphoric acid di-ester and salty reactionproducts thereof in the treatment layer and/or the phosphoric acid esterblend can be from 1:1 to 1:100.

The wording “molar ratio of the one or more phosphoric acid mono-esterand salty reaction products thereof to the one or more phosphoric aciddi-ester and salty reaction products thereof” in the meaning of thepresent invention refers to the sum of the molecular weight of thephosphoric acid mono-ester molecules and the sum of the molecular weightof the phosphoric acid mono-ester molecules in the salty reactionproducts thereof to the sum of the molecular weight of the phosphoricacid di-ester molecules and the sum of the molecular weight of thephosphoric acid di-ester molecules in the salty reaction productsthereof.

According to one embodiment the molar ratio of the one or morephosphoric acid mono-ester and salty reaction products thereof to theone or more phosphoric acid di-ester and salty reaction products thereofin the phosphoric acid ester blend is from 1:1 to 1:100, preferably from1:1.1 to 1:80, more preferably from 1:1.1 to 1:60, even more preferablyfrom 1:1.1 to 1:40, still even more preferably from 1:1.1 to 1:20, andmost preferably from 1:1.1 to 1:10.

Additionally or alternatively, the phosphoric acid ester blend of thetreatment layer comprises the one or more phosphoric acid mono-ester andsalty reaction products thereof in an amount of from 1 to 50 mol.-%,based on the molar sum of the one or more phosphoric acid mono-ester andsalty reaction products thereof and the one or more phosphoric aciddi-ester and salty reaction products thereof. For example, thephosphoric acid ester blend of the treatment layer comprises the one ormore phosphoric acid mono-ester and salty reaction products thereof inan amount of from 10 to 45 mol.-%, based on the molar sum of the one ormore phosphoric acid mono-ester and salty reaction products thereof andthe one or more phosphoric acid di-ester and salty reaction productsthereof.

According to one embodiment of the present invention,

-   -   I) the one or more phosphoric acid mono-ester consists of an        o-phosphoric acid molecule mono-esterified with one alcohol        molecule selected from unsaturated or saturated, branched or        linear, aliphatic or aromatic alcohols having a total amount of        carbon atoms from C6 to C30, preferably from C8 to C22, more        preferably from C8 to C20, and most preferably from C8 to C18 in        the alcohol substituent, and/or    -   II) the one or more phosphoric acid di-ester consists of an        o-phosphoric acid molecule di-esterified with two alcohol        molecules selected from the same or different, unsaturated or        saturated, branched or linear, aliphatic or aromatic fatty        alcohols having a total amount of carbon atoms from C6 to C30,        preferably from C8 to C22, more preferably from C8 to C20, and        most preferably from C8 to C18 in the alcohol substituent.

In one embodiment of the present invention, the phosphoric acid esterblend of the treatment layer further comprises one or more phosphoricacid tri-ester and/or phosphoric acid and salty reaction productsthereof.

The term “phosphoric acid tri-ester” in the meaning of the presentinvention refers to an o-phosphoric acid molecule tri-esterified withthree alcohol molecules selected from the same or different, unsaturatedor saturated, branched or linear, aliphatic or aromatic alcohols havinga total amount of carbon atoms from C6 to C30, preferably from C8 toC22, more preferably from C8 to C20 and most preferably from C8 to C18in the alcohol substituent.

It is appreciated that the expression “one or more” phosphoric acidtri-ester means that one or more kinds of phosphoric acid tri-ester maybe present on at least a part of the surface of the at least one groundcalcium carbonate-comprising filler material.

Accordingly, it should be noted that the one or more phosphoric acidtri-ester may be one kind of phosphoric acid tri-ester. Alternatively,the one or more phosphoric acid tri-ester may be a mixture of two ormore kinds of phosphoric acid tri-ester. For example, the one or morephosphoric acid tri-ester may be a mixture of two or three kinds ofphosphoric acid tri-ester, like two kinds of phosphoric acid tri-ester.

In one embodiment of the present invention, the one or more phosphoricacid tri-ester consists of an o-phosphoric acid molecule esterified withthree alcohols selected from the same or different, unsaturated orsaturated, branched or linear, aliphatic or aromatic alcohols having atotal amount of carbon atoms from C6 to C30 in the alcohol substituent.For example, the one or more phosphoric acid tri-ester consists of ano-phosphoric acid molecule esterified with three alcohols selected fromthe same or different, unsaturated or saturated, branched or linear,aliphatic or aromatic fatty alcohols having a total amount of carbonatoms from C8 to C22, more preferably from C8 to C20 and most preferablyfrom C8 to C18 in the alcohol substituent.

It is appreciated that the three alcohols used for esterifying thephosphoric acid may be independently selected from unsaturated orsaturated, branched or linear, aliphatic or aromatic alcohols having atotal amount of carbon atoms from C6 to C30 in the alcohol substituent.In other words, the one or more phosphoric acid tri-ester molecule maycomprise three substituents being derived from the same alcohols or thephosphoric acid tri-ester molecule may comprise three substituents beingderived from different alcohols.

In one embodiment of the present invention, the one or more phosphoricacid tri-ester consists of an o-phosphoric acid molecule esterified withthree alcohols selected from the same or different, saturated and linearor branched and aliphatic alcohols having a total amount of carbon atomsfrom C6 to C30 in the alcohol substituent. For example, the one or morephosphoric acid tri-ester consists of an o-phosphoric acid moleculeesterified with three alcohols selected from the same or different,saturated and linear or branched and aliphatic alcohols having a totalamount of carbon atoms from C8 to C22, more preferably from C8 to C20and most preferably from C8 to C18 in the alcohol substituent.

In one embodiment of the present invention, the one or more phosphoricacid tri-ester consists of an o-phosphoric acid molecule esterified withthree alcohols selected from saturated and linear and aliphatic alcoholshaving a total amount of carbon atoms from C6 to C30, preferably from C8to C22, more preferably from C8 to C20 and most preferably from C8 toC18 in the alcohol substituent. Alternatively, the one or morephosphoric acid tri-ester consists of an o-phosphoric acid moleculeesterified with three alcohols selected from saturated and branched andaliphatic alcohols having a total amount of carbon atoms from C6 to C30,preferably from C8 to C22, more preferably from C8 to C20 and mostpreferably from C8 to C18 in the alcohol substituent.

In one embodiment of the present invention, the one or more phosphoricacid tri-ester is selected from the group comprising hexyl phosphoricacid tri-ester, heptyl phosphoric acid tri-ester, octyl phosphoric acidtri-ester, 2-ethylhexyl phosphoric acid tri-ester, nonyl phosphoric acidtri-ester, decyl phosphoric acid tri-ester, undecyl phosphoric acidtri-ester, dodecyl phosphoric acid tri-ester, tetradecyl phosphoric acidtri-ester, hexadecyl phosphoric acid tri-ester, heptylnonyl phosphoricacid tri-ester, octadecyl phosphoric acid tri-ester,2-octyl-1-decylphosphoric acid tri-ester, 2-octyl-1-dodecylphosphoricacid tri-ester and mixtures thereof.

For example, the one or more phosphoric acid tri-ester is selected fromthe group comprising 2-ethylhexyl phosphoric acid tri-ester, hexadecylphosphoric acid tri-ester, heptylnonyl phosphoric acid tri-ester,octadecyl phosphoric acid tri-ester, 2-octyl-1-decylphosphoric acidtri-ester, 2-octyl-1-dodecylphosphoric acid tri-ester and mixturesthereof.

In one embodiment of the present invention, at least a part of thesurface of the at least one ground calcium carbonate-comprising fillermaterial comprises a phosphoric acid ester blend of one or morephosphoric acid mono-ester and salty reaction products thereof and oneor more phosphoric acid di-ester and salty reaction products thereof andone or more phosphoric acid tri-ester and optionally phosphoric acid andsalty reaction products thereof. For example, at least a part of thesurface of the at least one ground calcium carbonate-comprising fillermaterial comprises a phosphoric acid ester blend of the one or morephosphoric acid mono-ester and salty reaction products thereof and oneor more phosphoric acid di-ester and salty reaction products thereof andone or more phosphoric acid tri-ester and phosphoric acid and saltyreaction products thereof.

Alternatively, at least a part of the surface of the at least one groundcalcium carbonate-comprising filler material comprises a phosphoric acidester blend of the one or more phosphoric acid mono-ester and saltyreaction products thereof and one or more phosphoric acid di-ester andsalty reaction products thereof and optionally phosphoric acid and saltyreaction products thereof. For example, at least a part of the surfaceof the at least one ground calcium carbonate-comprising filler materialcomprises a phosphoric acid ester blend of the one or more phosphoricacid mono-ester and salty reaction products thereof and one or morephosphoric acid di-ester and salty reaction products thereof andphosphoric acid and salty reaction products thereof.

If at least a part of the surface of the at least one ground calciumcarbonate-comprising filler material comprises a phosphoric acid esterblend comprising one or more phosphoric acid tri-ester, it is preferredthat the phosphoric acid ester blend comprises the one or morephosphoric acid tri-ester in an amount of ≤10 mol.-%, based on the molarsum of the one or more phosphoric acid mono-ester and salty reactionproducts thereof and the one or more phosphoric acid di-ester and saltyreaction products thereof and one or more phosphoric acid tri-ester andthe phosphoric acid and salty reaction products thereof. For example,the phosphoric acid ester blend comprises the one or more phosphoricacid tri-ester in an amount of ≤8 mol.-%, preferably of ≤6 mol.-%, andmore preferably of ≤4 mol.-%, like from 0.1 to 4 mol.-%, based on themolar sum of the one or more phosphoric acid mono-ester and saltyreaction products thereof and the one or more phosphoric acid di-esterand salty reaction products thereof and one or more phosphoric acidtri-ester and the phosphoric acid and salty reaction products thereof.

Additionally or alternatively, if at least a part of the surface of theat least one ground calcium carbonate-comprising filler materialcomprises a phosphoric acid ester blend comprising phosphoric acid andsalty reaction products thereof, it is preferred that the phosphoricacid ester blend comprises the phosphoric acid and salty reactionproducts thereof in an amount of ≤10 mol.-%, based on the molar sum ofthe one or more phosphoric acid mono-ester and salty reaction productsthereof and the one or more phosphoric acid di-ester and salty reactionproducts thereof and one or more phosphoric acid tri-ester and thephosphoric acid and salty reaction products thereof. For example, thephosphoric acid ester blend comprises the phosphoric acid and saltyreaction products thereof in an amount of ≤8 mol.-%, preferably of ≤6mol.-%, and more preferably of ≤4 mol.-%, like from 0.1 to 4 mol.-%,based on the molar sum of the one or more phosphoric acid mono-ester andsalty reaction products thereof and the one or more phosphoric aciddi-ester and salty reaction products thereof and one or more phosphoricacid tri-ester and the phosphoric acid and salty reaction productsthereof.

If the phosphoric acid ester blend further comprises phosphoric acid andsalty reaction products thereof and one or more phosphoric acidtri-ester, it is thus preferred that the molar ratio of the phosphoricacid and salty reaction products thereof to the one or more phosphoricacid mono-ester and salty reaction products thereof to the one or morephosphoric acid di-ester and salty reaction products thereof to the oneor more phosphoric acid tri-ester in the phosphoric acid ester blend is≤10 mol.-%:≤40 mol.-%:≥40 mol. %:≤10 mol.-%, based on the molar sum ofthe one or more phosphoric acid mono-ester and salty reaction productsthereof and the one or more phosphoric acid di-ester and salty reactionproducts thereof and the one or more phosphoric acid tri-ester and thephosphoric acid and salty reaction products thereof.

The wording “molar ratio of the phosphoric acid and salty reactionproducts thereof to the one or more phosphoric acid mono-ester and saltyreaction products thereof to the one or more phosphoric acid di-esterand salty reaction products thereof to the one or more phosphoric acidtri-ester” in the meaning of the present invention refers to the sum ofthe molecular weight of the phosphoric acid and the sum of the molecularweight of the phosphoric acid molecules in the salty reaction productsthereof to the sum of the molecular weight of the phosphoric acidmono-ester molecules and the sum of the molecular weight of thephosphoric acid mono-ester molecules in the salty reaction productsthereof to the sum of the molecular weight of the phosphoric aciddi-ester molecules and the sum of the molecular weight of the phosphoricacid di-ester molecules in the salty reaction products thereof to thesum of the molecular weight of the phosphoric acid tri-ester molecules.

It is appreciated that the phosphoric acid ester blend may comprisesalty reaction products obtained from contacting the at least one fillermaterial, preferably the at least one ground calciumcarbonate-comprising filler material, with the one or more phosphoricacid mono-ester and one or more phosphoric acid di-ester and optionallyphosphoric acid. In such a case, the phosphoric acid ester blendpreferably comprises salty reaction products such as one or morecalcium, magnesium and/or aluminum salts of phosphoric acid mono-estersand one or more calcium, magnesium and/or aluminum salts of phosphoricacid di-ester and optionally one or more calcium, magnesium and/oraluminum salts of phosphoric acid. Preferably, the phosphoric acid esterblend comprises salty reaction products such as one or more calciumand/or magnesium salts of phosphoric acid mono-esters and one or morecalcium and/or magnesium salts of phosphoric acid di-ester andoptionally one or more calcium and/or magnesium salts of phosphoricacid.

In one embodiment of the present invention, the one or more phosphoricacid mono-ester and/or the one or more phosphoric acid di-ester andoptionally the phosphoric acid may be at least partially neutralized byone or more hydroxides of a mono and/or bi and/or trivalent cationand/or one or more salts of a weak acid of a mono and/or bi and/ortrivalent cation before the at least one filler material, preferably theat least one ground calcium carbonate-comprising filler material, isprepared. The one or more hydroxides of a bi and/or trivalent cation maybe selected from Ca(OH)₂, Mg(OH)₂, Al(OH)₃ and mixtures thereof.

Additionally or alternatively, if the one or more phosphoric acidmono-ester and/or the one or more phosphoric acid di-ester andoptionally the phosphoric acid is at least partially neutralized by oneor more hydroxides and/or one or more salts of a weak acid of amonovalent cation, the amount of monovalent cations is preferably ≤10mol.-%, based on the molar sum of acidic groups in the one or morephosphoric acid mono-ester and the one or more phosphoric acid di-esterand optionally the phosphoric acid, the one or more hydroxide and/or theone or more salt of a weak acid of a monovalent cation to neutralize maybe selected from LiOH, NaOH, KOH, Na₂CO₃, Li₂CO₃, K₂CO₃ and mixturesthereof.

In one embodiment of the present invention, the bivalent cations usedfor the partial neutralization of the one or more phosphoric acidmono-ester and/or the one or more phosphoric acid di-ester and optionalthe phosphoric acid are derived from salts of weak acids of suchcations, preferably from carbonates and/or borates, such as calciumcarbonate.

The term “weak acid” in the meaning of the present application refers toa Brønsted-Lowry acid, i.e. an H₃O⁺-ion provider, featuring a pK_(a)of >2, preferably from 4 to 7.

Accordingly, the phosphoric acid ester blend of the treatment layer mayfurther comprise salty reaction products such as one or more calciumand/or magnesium salts of phosphoric acid mono-esters and one or morecalcium and/or magnesium salts of phosphoric acid di-ester andoptionally one or more calcium and/or magnesium salts of phosphoricacid. Additionally or alternatively, the phosphoric acid ester blend ofthe treatment layer further comprises salty reaction products such asone or more aluminum salts of phosphoric acid mono-esters and one ormore aluminum salts of phosphoric acid di-ester and optionally one ormore aluminum salts of phosphoric acid. Additionally or alternatively,the phosphoric acid ester blend of the treatment layer further comprisessalty reaction products such as one or more lithium salts of phosphoricacid mono-esters and one or more lithium salts of phosphoric aciddi-ester and optionally one or more lithium salts of phosphoric acid.Additionally or alternatively, the phosphoric acid ester blend of thetreatment layer further comprises salty reaction products such as one ormore sodium salts of phosphoric acid mono-esters and one or more sodiumsalts of phosphoric acid di-ester and optionally one or more sodiumsalts of phosphoric acid. Additionally or alternatively, the phosphoricacid ester blend of the treatment layer further comprises salty reactionproducts such as one or more potassium salts of phosphoric acidmono-esters and one or more potassium salts of phosphoric acid di-esterand optionally one or more potassium salts of phosphoric acid.

If the one or more phosphoric acid mono-ester and/or the one or morephosphoric acid di-ester and optionally the phosphoric acid is at leastpartially neutralized by one or more hydroxides and/or one or more saltsof a weak acid of a monovalent cation, the treatment layer and/or thephosphoric acid ester blend preferably comprises an amount of monovalentcations of ≤10 mol.-%, based on the molar sum of acidic groups in theone or more phosphoric acid mono-ester and the one or more phosphoricacid di-ester and optionally the phosphoric acid.

In one embodiment of the present invention, the phosphoric acid esterblend of the treatment layer may further comprise additional surfacetreatment agents that do not correspond to the one or more phosphoricacid mono-ester, one or more phosphoric acid di-ester and the optionalone or more phosphoric acid tri-ester and/or phosphoric acid of thepresent invention.

In one embodiment, the molar ratio of the one or more phosphoric acidmono-ester and/or the one or more phosphoric acid di-ester to the saltyreaction products thereof is from 99.9:0.1 to 0.1:99.9, preferably from70:30 to 90:10.

The wording “molar ratio of the one or more phosphoric acid mono-esterand/or the one or more phosphoric acid di-ester to the salty reactionproducts thereof” in the meaning of the present invention refers to thesum of the molecular weight of the phosphoric acid mono-ester moleculesand/or the sum of the molecular weight of the phosphoric acid di-estermolecules to the sum of the molecular weight of the phosphoric acidmono-ester molecules in the salty reaction products thereof and/or thesum of the phosphoric acid di-ester molecules in the salty reactionproducts thereof.

Methods for preparing the surface-treated filler material producttreated with at least one phosphoric acid ester blend and suitablecompounds for coating are described e.g. in EP 2 770 017 A1, which isthus incorporated herewith by reference.

According to another embodiment of the present invention, thesurface-treated filler material product comprises a treatment layer onat least a part of the surface of the at least one ground calciumcarbonate-comprising filler material, wherein the treatment layercomprises at least one saturated aliphatic linear or branched carboxylicacid and salty reaction products thereof.

For example, the treatment layer comprises a saturated aliphatic linearor branched carboxylic acid having a total amount of carbon atoms fromC4 to C24 and/or salty reaction products thereof.

The term “salty reaction products” of the saturated aliphatic linear orbranched carboxylic acid in the meaning of the present invention refersto products obtained by contacting the at least one ground calciumcarbonate-comprising filler material with the at least one saturatedaliphatic linear or branched carboxylic acid. Said reaction products areformed between at least a part of the applied at least one saturatedaliphatic linear or branched carboxylic acid and reactive moleculeslocated at the surface of the at least one ground calciumcarbonate-comprising filler material.

The aliphatic carboxylic acid in the meaning of the present inventionmay be selected from one or more linear chain, branched chain,saturated, unsaturated and/or alicyclic carboxylic acids. Preferably,the aliphatic carboxylic acid is a monocarboxylic acid, i.e. thealiphatic carboxylic acid is characterized in that a single carboxylgroup is present. Said carboxyl group is placed at the end of the carbonskeleton.

In one embodiment of the present invention, the aliphatic linear orbranched carboxylic acid is selected from saturated unbranchedcarboxylic acids, that is to say the aliphatic carboxylic acid ispreferably selected from the group of carboxylic acids consisting ofpentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoicacid, decanoic acid, undecanoic acid, lauric acid, tridecanoic acid,myristic acid, pentadecanoic acid, palmitic acid, heptadecanoic acid,stearic acid, nonadecanoic acid, arachidic acid, heneicosylic acid,behenic acid, tricosylic acid, lignoceric acid and mixtures thereof.

In another embodiment of the present invention, the aliphatic linear orbranched carboxylic acid is selected from the group consisting ofoctanoic acid, decanoic acid, lauric acid, myristic acid, palmitic acid,stearic acid, arachidic acid and mixtures thereof. Preferably, thealiphatic linear or branched carboxylic acid is selected from the groupconsisting of octanoic acid, myristic acid, palmitic acid, stearic acidand mixtures thereof.

For example, the aliphatic linear or branched carboxylic acid isoctanoic acid or stearic acid. Preferably, the aliphatic linear orbranched carboxylic acid is stearic acid.

In one embodiment, the molar ratio of the at least one saturatedaliphatic linear or branched carboxylic acid to the salty reactionproduct(s) thereof is from 99.9:0.1 to 0.1:99.9, preferably from 70:30to 90:10.

The wording “molar ratio of the at least one saturated aliphatic linearor branched carboxylic acid to the salty reaction product(s) thereof” inthe meaning of the present invention refers to the sum of the molecularweight of the saturated aliphatic linear or branched carboxylic acid tothe sum of the molecular weight of the saturated aliphatic linear orbranched carboxylic acid in the salty reaction products.

According to another embodiment of the present invention, the surfacetreated filler material comprises a treatment layer on at least a partof the surface of the at least one ground calcium carbonate-comprisingfiller material, wherein the treatment layer comprises at least onealiphatic aldehyde and/or salty reaction products thereof.

In this regard, the at least one aliphatic aldehyde represents a surfacetreatment agent and may be selected from any linear, branched oralicyclic, substituted or non-substituted, saturated or unsaturatedaliphatic aldehyde. Said aldehyde is preferably chosen such that thenumber of carbon atoms is greater than or equal to 6 and more preferablygreater than or equal to 8. Furthermore, said aldehyde has generally anumber of carbon atoms that is lower or equal to 14, preferably lower orequal to 12 and more preferably lower or equal to 10. In one preferredembodiment, the number of carbon atoms of the aliphatic aldehyde isbetween 6 and 14, preferably between 6 and 12 and more preferablybetween 6 and 10.

In another preferred embodiment, the at least one aliphatic aldehyde ispreferably chosen such that the number of carbon atoms is between 6 and12, more preferably between 6 and 9, and most preferably 8 or 9.

The aliphatic aldehyde may be selected from the group of aliphaticaldehydes consisting of hexanal, (E)-2-hexenal, (Z)-2-hexenal,(E)-3-hexenal, (Z)-3-hexenal, (E)-4-hexenal, (Z)-4-hexenal, 5-hexenal,heptanal, (E)-2-heptenal, (Z)-2-heptenal, (E)-3-heptenal,(Z)-3-heptenal, (E)-4-heptenal, (Z)-4-heptenal, (E)-5-heptenal,(Z)-5-heptenal, 6-heptenal, octanal, (E)-2-octenal, (Z)-2-octenal,(E)-3-octenal, (Z)-3-octenal, (E)-4-octenal, (Z)-4-octenal,(E)-5-octenal, (Z)-5-octenal, (E)-6-octenal, (Z)-6-octenal, 7-octenal,nonanal, (E)-2-nonenal, (Z)-2-nonenal, (E)-3-nonenal, (Z)-3-nonenal,(E)-4-nonenal, (Z)-4-nonenal, (E)-5-nonenal, (Z)-5-nonenal,(E)-6-nonenal, (Z)-6-nonenal, (E)-6-nonenal, (Z)-6-nonenal,(E)-7-nonenal, (Z)-7-nonenal, 8-nonenal, decanal, (E)-2-decenal,(Z)-2-decenal, (E)-3-decenal, (Z)-3-decenal, (E)-4-decenal,(Z)-4-decenal, (E)-5-decenal, (Z)-5-decenal, (E)-6-decenal,(Z)-6-decenal, (E)-7-decenal, (Z)-7-decenal, (E)-8-decenal,(Z)-8-decenal, 9-decenal, undecanal, (E)-2-undecenal, (Z)-2-undecenal,(E)-3-undecenal, (Z)-3-undecenal, (E)-4-undecenal, (Z)-4-undecenal,(E)-5-undecenal, (Z)-5-undecenal, (E)-6-undecenal, (Z)-6-undecenal,(E)-7-undecenal, (Z)-7-undecenal, (E)-8-undecenal, (Z)-8-undecenal,(E)-9-undecenal, (Z)-9-undecenal, 10-undecenal, dodecanal,(E)-2-dodecenal, (Z)-2-dodecenal, (E)-3-dodecenal, (Z)-3-dodecenal,(E)-4-dodecenal, (Z)-4-dodecenal, (E)-5-dodecenal, (Z)-5-dodecenal,(E)-6-dodecenal, (Z)-6-dodecenal, (E)-7-dodecenal, (Z)-7-dodecenal,(E)-8-dodecenal, (Z)-8-dodecenal, (E)-9-dodecenal, (Z)-9-dodecenal,(E)-10-dodecenal, (Z)-10-dodecenal, 11-dodecenal, tridecanal,(E)-2-tridecenal, (Z)-2-tridecenal, (E)-3-tridecenal, (Z)-3-tridecenal,(E)-4-tridecenal, (Z)-4-tridecenal, (E)-5-tridecenal, (Z)-5-tridecenal,(E)-6-tridecenal, (Z)-6-tridecenal, (E)-7-tridecenal, (Z)-7-tridecenal,(E)-8-tridecenal, (Z)-8-tridecenal, (E)-9-tridecenal, (Z)-9-tridecenal,(E)-10-tridecenal, (Z)-10-tridecenal, (E)-11-tridecenal,(Z)-11-tridecenal, 12-tridecenal, butadecanal, (E)-2-butadecenal,(Z)-2-butadecenal, (E)-3-butadecenal, (Z)-3-butadecenal,(E)-4-butadecenal, (Z)-4-butadecenal, (E)-5-butadecenal,(Z)-5-butadecenal, (E)-6-butadecenal, (Z)-6-butadecenal,(E)-7-butadecenal, (Z)-7-butadecenal, (E)-8-butadecenal,(Z)-8-butadecenal, (E)-9-butadecenal, (Z)-9-butadecenal,(E)-10-butadecenal, (Z)-10-butadecenal, (E)-11-butadecenal,(Z)-11-butadecenal, (E)-12-butadecenal, (Z)-12-butadecenal,13-butadecenal, and mixtures thereof. In a preferred embodiment, thealiphatic aldehyde is selected from the group consisting of hexanal,(E)-2-hexenal, (Z)-2-hexenal, (E)-3-hexenal, (Z)-3-hexenal,(E)-4-hexenal, (Z)-4-hexenal, 5-hexenal, heptanal, (E)-2-heptenal,(Z)-2-heptenal, (E)-3-heptenal, (Z)-3-heptenal, (E)-4-heptenal,(Z)-4-heptenal, (E)-5-heptenal, (Z)-5-heptenal, 6-heptenal, octanal,(E)-2-octenal, (Z)-2-octenal, (E)-3-octenal, (Z)-3-octenal,(E)-4-octenal, (Z)-4-octenal, (E)-5-octenal, (Z)-5-octenal,(E)-6-octenal, (Z)-6-octenal, 7-octenal, nonanal, (E)-2-nonenal,(Z)-2-nonenal, (E)-3-nonenal, (Z)-3-nonenal, (E)-4-nonenal,(Z)-4-nonenal, (E)-5-nonenal, (Z)-5-nonenal, (E)-6-nonenal,(Z)-6-nonenal, (E)-7-nonenal, (Z)-7-nonenal, 8-nonenal and mixturesthereof.

In another preferred embodiment, the at least one aliphatic aldehyde isa saturated aliphatic aldehyde. In this case the aliphatic aldehyde isselected from the group consisting of hexanal, heptanal, octanal,nonanal, decanal, undecanal, dodecanal, tridecanal, butadecanal andmixtures thereof. Preferably, the at least one aliphatic aldehyde in theform of a saturated aliphatic aldehyde is selected from the groupconsisting of hexanal, heptanal, octanal, nonanal, decanal, undecanal,dodecanal and mixtures thereof. For instance, the at least one aliphaticaldehyde in the form of a saturated aliphatic aldehyde is selected fromoctanal, nonanal and mixtures thereof.

If a mixture of two aliphatic aldehydes, e.g. two saturated aliphaticaldehydes such as octanal and nonanal is used according to the presentinvention, the weight ratio of octanal and nonanal is from 70:30 to30:70 and more preferably from 60:40 to 40:60.

In one especially preferred embodiment of the present invention, theweight ratio of octanal and nonanal is about 1:1.

The term “salty reaction products” of the at least one aliphaticaldehyde in the meaning of the present invention refers to productsobtained by contacting the at least one ground calciumcarbonate-comprising filler material with the at least one aliphaticaldehyde. Said reaction products are formed between at least a part ofthe applied at least one aliphatic aldehyde and reactive moleculeslocated at the surface of the at least one filler material, preferablythe at least one ground calcium carbonate-comprising filler material.

In one embodiment, the molar ratio of the at least one aliphaticaldehyde to the salty reaction product(s) thereof is from 99.9:0.1 to0.1:99.9, preferably from 70:30 to 90:10.

The wording “molar ratio of the at least one aliphatic aldehyde to thesalty reaction product(s) thereof” in the meaning of the presentinvention refers to the sum of the molecular weight of the aliphaticaldehyde to the sum of the molecular weight of the aliphatic aldehyde inthe salty reaction products.

Methods for preparing the surface-treated filler material producttreated with at least one aliphatic aldehyde and suitable compounds forcoating are described e.g. in EP 2 390 285 A1, which is thusincorporated herewith by reference.

According to another embodiment of the present invention, the surfacetreated filler material comprises a treatment layer on at least a partof the surface of the at least one ground calcium carbonate-comprisingfiller material, wherein the treatment layer comprises at least onemono-substituted succinic anhydride consisting of succinic anhydridemono-substituted with a group selected from a linear, branched,aliphatic and cyclic group having a total amount of carbon atoms from atleast C₂ to C₃₀ in the substituent and/or salty reaction productsthereof.

The term “succinic anhydride”, also called dihydro-2,5-furandione,succinic acid anhydride or succinyl oxide, has the molecular formulaC₄H₄O₃ and is the acid anhydride of succinic acid.

The term “mono-substituted” succinic anhydride in the meaning of thepresent invention refers to a succinic anhydride wherein a hydrogen atomis substituted by another substituent.

The term “mono-substituted” succinic acid in the meaning of the presentinvention refers to a succinic acid wherein a hydrogen atom issubstituted by another substituent.

The term “salty reaction products” of the at least one mono-substitutedsuccinic anhydride refers to products obtained by contacting the atleast one ground calcium carbonate-comprising filler material with oneor more mono-substituted succinic anhydride(s). Said salty reactionproducts are formed between the mono-substituted succinic acid which isformed from the applied mono-substituted succinic anhydride and reactivemolecules located at the surface of the at least one ground calciumcarbonate-comprising filler material. Alternatively, said salty reactionproducts are formed between the mono-substituted succinic acid, whichmay optionally be present with the at least one mono-substitutedsuccinic anhydride, and reactive molecules located at the surface of theat least one ground calcium carbonate-comprising filler material.

For example, the treatment layer on the surface of the at least oneground calcium carbonate-comprising filler material comprises at leastone mono-substituted succinic anhydride consisting of succinic anhydridemono-substituted with a group selected from a linear, branched,aliphatic and cyclic group having a total amount of carbon atoms from atleast C₂ to C₃₀ in the substituent and/or salty reaction productsthereof. More preferably, the treatment layer on the surface of the atleast one ground calcium carbonate-comprising filler material comprisesat least one mono-substituted succinic anhydride consisting of succinicanhydride mono-substituted with a group selected from a linear,branched, aliphatic and cyclic group having a total amount of carbonatoms from at least C₃ to C₃₀, even more preferably from at least C₃ toC₂₀ and most preferably from C₄ to C₁₈ in the substituent and/or saltyreaction products thereof.

More precisely, the treatment layer on the surface of the at least oneground calcium carbonate-comprising filler material comprises at leastone mono-substituted succinic anhydride consisting of succinic anhydridemono-substituted with a group being a linear and aliphatic group havinga total amount of carbon atoms from at least C₂ to C₃₀, preferably fromat least C₃ to C₃₀, more preferably from at least C₃ to C₂₀ and mostpreferably from C₄ to C₁₈ in the substituent and/or salty reactionproducts thereof. Additionally or alternatively, the treatment layer onthe surface of the at least one ground calcium carbonate-comprisingfiller material comprises at least one mono-substituted succinicanhydride consisting of succinic anhydride mono-substituted with a groupbeing a branched and aliphatic group having a total amount of carbonatoms from at least C₃ to C₃₀, preferably from at least C₄ to C₃₀, morepreferably from at least C₄ to C₂₀ and most preferably from C₄ to C₁₈ inthe substituent and/or salty reaction products thereof. Additionally oralternatively, the treatment layer on the surface of the at least oneground calcium carbonate-comprising filler material comprises at leastone mono-substituted succinic anhydride consisting of succinic anhydridemono-substituted with a group being an aliphatic and cyclic group havinga total amount of carbon atoms from at least C₅ to C₃₀, preferably fromat least C₅ to C₂₀ and most preferably from C₅ to C₁₈ in the substituentand/or salty reaction products thereof.

Methods for preparing the surface-treated filler material producttreated with at least one mono-substituted succinic anhydride consistingof succinic anhydride mono-substituted with a group selected from alinear, branched, aliphatic and cyclic group having a total amount ofcarbon atoms from at least C₂ to C₃₀ in the substituent and suitablecompounds for coating are described e.g. in WO 2016/023937 A1, which isthus incorporated herewith by reference.

According to another embodiment of the present invention, the surfacetreated filler material product comprises a treatment layer on at leasta part of the surface of the at least one ground calciumcarbonate-comprising filler material, wherein the treatment layercomprises at least one polydialkylsiloxane.

Preferred polydialkylsiloxanes are described e.g. in US 2004/0097616 A1.Most preferred are polydialkylsiloxanes selected from the groupconsisting of polydimethylsiloxane, preferably dimethicone,polydiethylsiloxane and polymethylphenylsiloxane and/or mixturesthereof.

For example, the at least one polydialkylsiloxane is preferably apolydimethylsiloxane (PDMS).

The at least one polydialkylsiloxane is preferably present in a quantitysuch that the total amount of said polydialkylsiloxane on at least apart of the surface of the at least one ground calciumcarbonate-comprising filler material, is less than 1 000 ppm, morepreferably less than 800 ppm and most preferably less than 600 ppm. Forexample, the total amount of the polydialkylsiloxane on at least a partof the surface of the at least one ground calcium carbonate-comprisingfiller material, is from 100 to 1 000 ppm, more preferably from 200 to800 ppm and most preferably from 300 to 600 ppm, e.g. from 400 to 600ppm.

The treatment layer on the surface of the at least one ground calciumcarbonate-comprising filler material preferably comprises at least onesaturated aliphatic linear or branched carboxylic acid and saltyreaction products thereof, and/or at least one mono-substituted succinicanhydride consisting of succinic anhydride mono-substituted with a groupselected from a linear, branched, aliphatic and cyclic group having atotal amount of carbon atoms from at least C₂ to C₃₀ in the substituentand/or salty reaction products thereof. More preferably, the treatmentlayer on the surface of the at least one ground calciumcarbonate-comprising filler material comprises at least one saturatedaliphatic linear or branched carboxylic acid and salty reaction productsthereof.

In one embodiment, the treatment layer on at least a part of the surfaceof the at least one ground calcium carbonate-comprising filler materialcomprises a mixture of the above materials, preferably a mixture of twomaterials.

Thus, an after treatment layer may be present on the treatment layer.

An “after treatment layer” in the meaning of the present inventionrefers to a layer, preferably a monolayer of a surface treatment agentwhich can be different from the treatment layer, the “after treatmentlayer” is located on the “treatment layer”.

In one preferred embodiment the surface treatment of the at least oneground calcium carbonate-comprising filler material is carried out intwo steps, the first step comprising a treatment by a phosphoric acidester blend of one or more phosphoric acid mono-ester and/or one or morephosphoric acid di-ester or at least one saturated aliphatic linear orbranched carboxylic acid or at least one aliphatic aldehyde or at leastone mono-substituted succinic anhydride consisting of succinic anhydridemono-substituted with a group selected from a linear, branched,aliphatic and cyclic group having a total amount of carbon atoms from atleast C₂ to C₃₀ in the substituent for forming a treatment layer and thesecond step comprising a treatment by at least one polydialkylsiloxanefor forming an after treatment layer.

In another embodiment the surface treatment is carried out by treatingthe at least one ground calcium carbonate-comprising filler materialsimultaneously with a phosphoric acid ester blend of one or morephosphoric acid mono-ester and/or one or more phosphoric acid di-esteror at least one saturated aliphatic linear or branched carboxylic acidor at least one aliphatic aldehyde or at least one mono-substitutedsuccinic anhydride consisting of succinic anhydride mono-substitutedwith a group selected from a linear, branched, aliphatic and cyclicgroup having a total amount of carbon atoms from at least C₂ to C₃₀ inthe substituent and at least one polydialkylsiloxane for forming atreatment layer.

Furthermore, the surface treatment can be carried out by treating the atleast one ground calcium carbonate-comprising filler material first witha polydialkylsiloxane and subsequently with phosphoric acid ester blendof one or more phosphoric acid mono-ester and/or one or more phosphoricacid di-ester or at least one saturated aliphatic linear or branchedcarboxylic acid or at least one aliphatic aldehyde or at least onemono-substituted succinic anhydride consisting of succinic anhydridemono-substituted with a group selected from a linear, branched,aliphatic and cyclic group having a total amount of carbon atoms from atleast C₂ to C₃₀ in the substituent.

Preferably, the after treatment layer comprises at least onepolydialkylsiloxane.

Thus, the treatment layer on at least a part of the surface of the atleast one ground calcium carbonate-comprising filler material preferablycomprises a phosphoric acid ester blend of one or more phosphoric acidmono-ester and salty reaction products thereof and/or one or morephosphoric acid di-ester and salty reaction products thereof and theafter treatment layer comprises at least one polydialkylsiloxane.

Alternatively, the treatment layer on at least a part of the surface ofthe at least one ground calcium carbonate-comprising filler materialcomprises at least one saturated aliphatic linear or branched carboxylicacid and salty reaction products thereof and the after treatment layercomprises at least one polydialkylsiloxane.

Alternatively, the treatment layer on at least a part of the surface ofthe at least one ground calcium carbonate-comprising filler materialcomprises at least one aliphatic aldehyde and/or salty reaction productsthereof and the after treatment layer comprises at least onepolydialkylsiloxane.

Alternatively, the treatment layer on at least a part of the surface ofthe at least one ground calcium carbonate-comprising filler materialcomprises at least one mono-substituted succinic anhydride consisting ofsuccinic anhydride mono-substituted with a group selected from a linear,branched, aliphatic and cyclic group having a total amount of carbonatoms from at least C₂ to C₃₀ in the substituent and/or salty reactionproducts thereof and the after treatment layer comprises at least onepolydialkylsiloxane.

More preferably, the treatment layer on at least a part of the surfaceof the at least one ground calcium carbonate-comprising filler materialcomprises, most preferably consists of, at least one saturated aliphaticlinear or branched carboxylic acid and salty reaction products thereofor at least one mono-substituted succinic anhydride consisting ofsuccinic anhydride mono-substituted with a group selected from a linear,branched, aliphatic and cyclic group having a total amount of carbonatoms from at least C₂ to C₃₀ in the substituent and/or salty reactionproducts thereof and the after treatment layer comprises, morepreferably consists of, at least one polydialkylsiloxane. For example,the treatment layer on at least a part of the surface of the at leastone ground calcium carbonate-comprising filler material comprises, mostpreferably consists of, at least one saturated aliphatic linear orbranched carboxylic acid and salty reaction products thereof and theafter treatment layer comprises, more preferably consists of, at leastone polydialkylsiloxane.

According to one embodiment the salty reaction product(s) of thephosphoric acid ester, the blend of one or more phosphoric acidmono-ester, the one or more phosphoric acid di-ester or the at least onesaturated aliphatic linear or branched carboxylic acid, the at least onealiphatic aldehyde, or at least one mono-substituted succinic anhydrideare one or more calcium and/or magnesium salts thereof.

Thus, it is appreciated that the at least one ground calciumcarbonate-comprising filler material product comprises, and preferablyconsists of, at least one ground calcium carbonate-comprising fillermaterial and a treatment layer comprising

-   -   i. a phosphoric acid ester blend of one or more phosphoric acid        mono-ester and salty reaction products thereof and/or one or        more phosphoric acid di-ester and salty reaction products        thereof, and/or    -   ii. at least one saturated aliphatic linear or branched        carboxylic acid and salty reaction products thereof, and/or    -   iii. at least one aliphatic aldehyde and/or salty reaction        products thereof, and/or    -   iv. at least one mono-substituted succinic anhydride consisting        of succinic anhydride mono-substituted with a group selected        from a linear, branched, aliphatic and cyclic group having a        total amount of carbon atoms from at least C₂ to C₃₀ in the        substituent and/or salty reaction products thereof, and/or    -   v. at least one polydialkylsiloxane, and/or    -   vi. mixtures of the materials according to i. to v.

The treatment layer is formed on the surface of said at least one groundcalcium carbonate-comprising filler material.

It is one requirement of the present invention that the surface-treatedfiller material product comprises the treatment layer in an amount from0.1 to 2.3 wt.-%, based on the total dry weight of the at least oneground calcium carbonate-comprising filler material.

According to one embodiment the surface-treated filler material productcomprises the treatment layer in an amount of from 0.2 to 2.0 wt.-%,preferably from 0.4 to 1.9 wt.-% and most preferably from 0.5 to 1.8wt.-%, based on the total dry weight of the at least one ground calciumcarbonate-comprising filler material.

The treatment layer is preferably characterized in that the total weightof the phosphoric acid ester blend of one or more phosphoric acidmono-ester and salty reaction products thereof and/or one or morephosphoric acid di-ester and salty reaction products thereof, and/or atleast one saturated aliphatic linear or branched carboxylic acid andsalty reaction products thereof, and/or at least one aliphatic aldehydeand/or salty reaction products thereof, and/or at least onemono-substituted succinic anhydride consisting of succinic anhydridemono-substituted with a group selected from a linear, branched,aliphatic and cyclic group having a total amount of carbon atoms from atleast C₂ to C₃₀ in the substituent and/or salty reaction productsthereof, and/or at least one polydialkylsiloxane, and/or mixtures ofsaid materials on the surface of the surface-treated filler materialproduct is from 0.05 to 1 wt.-%/m², more preferably from 0.1 to 0.5wt.-%/m² and most preferably from 0.15 to 0.25 wt.-%/m² of the at leastone ground calcium carbonate-comprising filler material.

In one embodiment of the present invention, the treatment layer ischaracterized in that the total weight of the phosphoric acid esterblend of one or more phosphoric acid mono-ester and salty reactionproducts thereof and/or one or more phosphoric acid di-ester and saltyreaction products thereof, and/or at least one saturated aliphaticlinear or branched carboxylic acid and salty reaction products thereof,and/or at least one aliphatic aldehyde and/or salty reaction productsthereof, and/or at least one mono-substituted succinic anhydrideconsisting of succinic anhydride mono-substituted with a group selectedfrom a linear, branched, aliphatic and cyclic group having a totalamount of carbon atoms from at least C₂ to C₃₀ in the substituent and/orsalty reaction products thereof, and/or at least onepolydialkylsiloxane, and/or mixtures of said materials on the surface ofthe surface-treated filler material product is from 0.1 to 5 mg/m², morepreferably from 0.25 to 4.5 mg/m² and most preferably from 1.0 to 4.0mg/m² of the at least one calcium carbonate-comprising material.

It is appreciated that the surface-treated filler material productpreferably features a volatile onset temperature ≥250° C. For example,the surface-treated filler material product features a volatile onsettemperature ≥260° C. or ≥270° C. In one embodiment, the surface-treatedfiller material product features a volatile onset temperature of 250° C.to 400° C., preferably from 260° C. to 400° C. and most preferably from270° C. to 400° C.

Additionally or alternatively, the surface-treated filler materialproduct features a total volatiles between 25 and 350° C. of less than0.25% by mass, and preferably of less than 0.23% by mass, e.g. of from0.04 to 0.21% by mass, preferably from 0.08 to 0.15% by mass, morepreferably from 0.1 to 0.12% by mass.

Furthermore, the surface-treated filler material product features a lowwater pick up susceptibility. It is preferred that the moisture pick upsusceptibility of the surface-treated filler material product is suchthat its total surface moisture level is less than 1 mg/g of dry calciumcarbonate-comprising filler material, at a temperature of about +23° C.(±2° C.). For example, the surface-treated filler material product has amoisture pick up susceptibility of from 0.1 to 1 mg/g, more preferablyof from 0.2 to 0.9 mg/g and most preferably of from 0.2 to 0.8 mg/g ofdry calcium carbonate-comprising material after at a temperature of +23C (±2° C.).

Additionally or alternatively, the surface-treated filler materialproduct has a hydrophilicity of below 8:2 volumetric ratio ofwater:ethanol measured at +23° C. (±2° C.) with the sedimentationmethod. For example, the surface-treated filler material product has ahydrophilicity of below 7:3 volumetric ratio of water:ethanol measuredat +23° C. (±2° C.) with the sedimentation method.

It is appreciated that the at least one layer of the mono or multi-layerpolyester film comprises the surface-treated filler material product inespecially high contents. Thus, the at least one layer of the mono ormulti-layer polyester film comprises the surface-treated filler materialproduct in an amount from >30 to 80.0 wt.-%, based on the total weightof the layer.

According to one embodiment, the at least one layer of the mono ormulti-layer polyester film comprises the surface-treated filler materialproduct in an amount from 30.01 to 80.0 wt.-%, based on the total weightof the layer, preferably from 30.1 to 78.0 wt.-%, more preferably from30.5 to 75.0 wt.-%, even more preferably from 31.0 to 73.0 wt.-%, andmost preferably from 35.0 to 70.0 wt.-%.

According to one aspect of the present invention, the surface-treatedfiller material product described above is used as voiding agent in amono or multi-layer polyester film.

Mono or Multi-Layer Polyester Film

According to the present invention a mono or multi-layer polyester filmis provided, wherein at least one layer of the film comprises at leastone polyester in an amount ranging from 20.0 to <70 wt.-% and asurface-treated filler material product in an amount ranging from >30 to80.0 wt.-%, based on the total weight of the layer, wherein thesurface-treated filler material product comprises

-   -   A) at least one ground calcium carbonate-comprising filler        material having a weight median particle size d₅₀ in the range        from 0.5 μm to 3.0 μm, and    -   B) a treatment layer on the surface of the at least one ground        calcium carbonate-comprising filler material comprising        -   i. a phosphoric acid ester blend of one or more phosphoric            acid mono-ester and salty reaction products thereof and/or            one or more phosphoric acid di-ester and salty reaction            products thereof, and/or        -   ii. at least one saturated aliphatic linear or branched            carboxylic acid and salty reaction products thereof, and/or        -   iii. at least one aliphatic aldehyde and/or salty reaction            products thereof, and/or        -   iv. at least one mono-substituted succinic anhydride            consisting of succinic anhydride mono-substituted with a            group selected from a linear, branched, aliphatic and cyclic            group having a total amount of carbon atoms from at least C₂            to C₃₀ in the substituent and/or salty reaction products            thereof, and/or        -   v. at least one polydialkylsiloxane, and/or        -   vi. mixtures of the materials according to i. to v.,    -   wherein the surface-treated filler material product comprises        the treatment layer in an amount of from 0.1 to 2.3 wt.-%, based        on the total dry weight of the at least one ground calcium        carbonate-comprising filler material.

As already mentioned above, it has been advantageously found out that amono or multi-layer polyester film can be prepared having an especiallyhigh filler content, i.e. a high content of the surface-treated fillermaterial product. Thus, it is appreciated that the at least onepolyester and surface-treated filler material product comprising layercomprises the surface-treated filler material product in an amountfrom >30 to 80.0 wt.-%, based on the total weight of the layer,preferably from 30.01 to 80.0 wt.-%, more preferably from 30.1 to 78.0wt.-%, still more preferably from 30.5 to 75.0 wt.-%, even morepreferably from 31.0 to 73.0 wt.-%, and most preferably from 35.0 to70.0 wt.-%.

The mono or multi-layer polyester film can be any kind of polyesterfilm. Preferably, the mono or multi-layer polyester film is a cast film,blown film, a double bubble film or a mono axially oriented polyesterfilm. More preferably, the mono or multi-layer polyester film is a castfilm or a mono axially oriented polyester film. Most preferably, themono or multi-layer polyester film is a mono axially oriented polyesterfilm.

For example, the term “mono axially oriented” polyester film refers to afilm that is obtained by stretching a cast film in only one directionamong machine direction (MD) or transverse direction (TD).

The mono or multi-layer polyester film especially features a lowdensity; especially compared to a film being free of the surface-treatedfiller material product. Thus, the mono or multi-layer polyester film,especially the at least one polyester and surface-treated fillermaterial product comprising layer, preferably has a density from 1.8 to2.4 g/cm³, preferably from 1.8 to 2.35 g/cm³, more preferably from 1.85to 2.3 g/cm³ and most preferably from 1.9 to 2.25 g/m².

According to one embodiment, the median thickness of the mono ormulti-layer polyester film, especially the at least one polyester andsurface-treated filler material product comprising layer, is from 0.5 to2 000 μm, preferably from 4 to 1 500 μm, more preferably from 5 to 1 300μm and most preferably from 6 to 1 000 μm, e.g. from 8 to 500 μm.

According to one embodiment, the mono or multi-layer polyester film,especially the at least one polyester and surface-treated fillermaterial product comprising layer, has a median thickness from 0.5 to 2000 μm, preferably from 4 to 1 500 μm, more preferably from 5 to 1 300μm and most preferably from 6 to 1 000 μm, e.g. from 8 to 500 μm, and adensity from 1.8 to 2.4 g/cm³, preferably from 1.8 to 2.35 g/cm³, morepreferably from 1.85 to 2.3 g/cm³ and most preferably from 1.9 to 2.25g/m².

It is appreciated that the polyester film is a mono or multi-layer film.

In case of a multi-layer polyester film, the film consists of two ormore layers such as two to ten layers, preferably three layers, whichare adjacent, i.e. in direct contact, to each other. If the multi-layerfilm is a three layer film, the film preferably has the film structureA-B-A or A-B-C. In the multi-layer film, the core layer is preferablyvoided, i.e. the layer comprising the at least one polyester and thesurface-treated filler material product. In one embodiment, themulti-layer film comprises a barrier layer which is located between twoadjacent layers. The “barrier layer” in the meaning of the presentapplication refers to a diffusion barrier, e.g. an oxygen and/or watervapor barrier, which is used for protecting the packed goods fromvarious external influences.

The barrier layer can be of any material known in the art as beingsuitable for this purpose. For example, the barrier layer can be analuminum layer, Al₂O₃ layer, SiO_(x) layer, ethylene vinyl alcohollayer, poly(vinyl alcohol) layer, polyvinylidene chloride layer,polypropylene layer, preferably an oriented polypropylene layer, apolyethylene layer, preferably an oriented polyethylene layer, apolyester barrier layer, e.g. those sold under the HOSTAPHAN® brand, andmixtures thereof.

It is appreciated that the median thickness of the mono or multi-layerpolyester film, especially of the layer comprising the surface-treatedfiller material product, may vary in a broad range depending on theproduct to be produced.

For example, the at least one polyester and surface-treated fillermaterial product comprising layer, is preferably of higher thicknessthan the other individual layers, i.e. the layers not containing the atleast one polyester and/or the surface-treated filler material product.Alternatively, the at least one polyester and surface-treated fillermaterial product comprising layer is of about the same thickness thanthe other layers together, i.e. the layers not containing the at leastone polyester and/or the surface-treated filler material product,preferably the at least one polyester and the surface-treated fillermaterial product.

Preferably, the mono or multi-layer polyester film, especially the atleast one polyester and surface-treated filler material productcomprising layer, has a median thickness from 0.5 to 2 000 μm,preferably from 4 to 1 500 μm, more preferably from 5 to 1 300 μm andmost preferably from 6 to 1 000 μm, e.g. from 8 to 500 μm.

The mono or multi-layer polyester film, especially the at least onepolyester and surface-treated filler material product comprising layer,is advantageous as it is a well-balanced microporous film/layer. That isto say, a microporous film or layer is provided, i.e. by controlling theformation of voids, having low density and opaque appearance at highfiller content.

Thus, the mono or multi-layer polyester film, especially the at leastone polyester and surface-treated filler material product comprisinglayer, preferably has

-   -   a) a density in the range from 1.8 to 2.4 g/cm³, preferably from        1.8 to 2.35 g/cm³, more preferably from 1.85 to 2.3 g/cm³ and        most preferably from 1.9 to 2.25 g/m², and/or    -   b) an opacity of ≥50%, preferably of ≥55% and most preferably of        ≥60%.

For example, the mono or multi-layer polyester film, especially the atleast one polyester and surface-treated filler material productcomprising layer, preferably has

-   -   a) a density in the range from 1.8 to 2.4 g/cm³, preferably from        1.8 to 2.35 g/cm³, more preferably from 1.85 to 2.3 g/cm³ and        most preferably from 1.9 to 2.25 g/m², or    -   b) an opacity of ≥50%, preferably of ≥55% and most preferably of        ≥60%.

If not otherwise indicated, the mechanical and optical propertiesdescribed herein refer to a polyester and surface-treated fillermaterial product comprising layer or film prepared in accordance withthe example section set out herein below, i.e. by using a biaxial labstretcher (Model Maxi Grip 750S Bi-axial Laboratory Stretching Frame,from Dr. Collin GmbH, Germany) under the described conditions. It isthus appreciated that the results for a polyester and surface-treatedfiller material product comprising layer or film prepared underdiffering conditions may deviate from the mechanical and opticalproperties defined herein.

Furthermore, the mono or multi-layer polyester film, especially the atleast one polyester and surface-treated filler material productcomprising layer, is advantageous as the mechanical properties of thefilm, especially the layer, are kept on a high level.

Furthermore, it is appreciated that the mono or multi-layer polyesterfilm, preferably the at least one layer comprising the surface-treatedfiller material product, is microporous and has good optical properties.

According to one embodiment the at least one polyester andsurface-treated filler material product comprising layer of the mono ormulti-layer polyester film further comprises a thermoplastic polymer,preferably crosslinked with a crosslinking agent. The thermoplasticpolymer is preferably selected from the group consisting of apolyolefin, a cyclic olefin copolymer (COC), a polyketone, apolysulphone, a fluoropolymer, a polyacetal, an ionomer, an acrylicresin, a polystyrene resin, a polyurethane, a polyamide, apolycarbonate, a polyacrylonitrile and a copolymerized resin andmixtures thereof.

Thus, if the mono or multi-layer polyester film comprises athermoplastic polymer, the thermoplastic polymer is present in the samelayer as the at least one polyester and the surface-treated fillermaterial product.

It is appreciated that the presence of the thermoplastic polymer in theat least one polyester and surface-treated filler material productcomprising layer of the mono or multi-layer polyester film isadvantageous as it acts as organic voiding agent and thus improves theformation of voids during the preparation of the film or layer. However,the thermoplastic polymer does typically not help to increase the opaqueappearance of the film or layer.

It is to be noted that the thermoplastic polymer is not soluble in theat least one polyester. Thus, the at least one polyester forms acontinuous phase, i.e. a matrix, and dispersed therein is thethermoplastic polymer, i.e. forms a dispersed phase.

Polyolefins that may be used are preferably selected from the groupconsisting of polypropylene, polyethylene, polybutylene, and mixturesthereof.

The polyolefin may be a copolymer or a homopolymer, the latter beingespecially preferred.

In case the polyolefin is a copolymer, the polyolefin is preferablyselected from the group comprising ethylene vinyl acetate, ethylenevinyl alcohol copolymer, ethylene methyl acrylate copolymer, ethylenebutyl acrylate copolymer, ethylene acrylic acid copolymer, and mixturesthereof.

In one embodiment, the thermoplastic polymer is a polypropylene,preferably a propylene homopolymer.

The thermoplastic polymer being a polyolefin preferably has a melt flowrate MFR₂ (230° C.; 2.16 kg) measured according to ISO 1133 in the rangefrom 1 to 20 g/10 min, preferably from 1 to 15 g/10 min, more preferablyfrom 1 to 10 g/10 min and most preferably from 1 to 5 g/10 min.

Additionally or alternatively, the thermoplastic polymer being apolyolefin has preferably a density of <0.920 g/cm³, more preferably<0.910 g/cm³, even more preferably in the range from 0.800 to 0.920g/cm³, yet more preferably from 0.850 to 0.910 g/cm³ and most preferablyfrom 0.880 to 0.910 g/cm³.

If polyolefins such as polypropylene are used as a voiding agent, it isto be noted that the polyolefins often do not disperse well and mayrequire a compatibilizer such as, for example, a carboxylatedpolyethylene to obtain a uniform distribution of voids. When used withthe at least one polyester to produce voided films, polyolefins alsotend to lower the polyester film surface tension and thereby reduce theprintability of the film. Polyolefins are softer than the at least onepolyester at room temperature which sometimes lowers the overall filmmodulus to unacceptable levels. Finally, polyolefins are relativelyinefficient voiding agents and large amounts are required to achieve thenecessary density reduction, which leads to poor surface roughness andprinting problems, thus making it difficult to use polyolefins in singlelayer films.

The cyclic olefin copolymer (COC) in the meaning of the presentinvention refers to a copolymer of ethylene and at least one cyclicolefin selected from the group consisting of bicycloalkene andtricycloalkene.

Typical examples of the cyclic olefin copolymer (COC) includebicyclo[2.2.1]hept-2-ene, 6-methylbicyclo[2.2.1]hept-2-ene,5,6-dimethylbicyclo[2.2.1]hept-2-ene, 1-methylbicyclo[2.2.1]hept-2-ene,6-ethylbicyclo[2.2.1]hept-2-ene, 6-n-butylbicyclo[2.2.1]hept-2-ene,6-i-butylbicyclo[2.2.1]hept-2-ene, 7-methylbicyclo[2.2.1]hept-2-ene,tricyclo[4.3.0.1^(2,5)]-3-decene,2-methyl-tricyclo[4.3.0.1^(2,5)]-3-decene,5-methyl-tricyclo[4.3.0.1^(2,5)]-3-decene,tricyclo[4.4.0.1^(2,5)]-3-decene and10-methyl-tricyclo[4.4.0.1^(2,5)]-3-decene.

A polyamide that may be used is preferably a polyamide 6 (also namednylon 6) or polyamide 66 (also named nylon 66).

For example, the thermoplastic polymer is a polypropylene, preferably apropylene homopolymer,

The at least one polyester and surface-treated filler material productcomprising layer of the mono or multi-layer polyester film comprises thethermoplastic polymer in an amount ranging from 0.1 to 29.9 wt.-%,preferably from 1 to 28 wt.-%, more preferably from 2 to 26 wt.-%, evenmore preferably from 3 to 25 wt.-%, still more preferably from 4.5 to 23wt.-%, and most preferably from 4 wt.-% to 20 wt.-%, based on the totalweight of the layer.

In one embodiment, the at least one polyester and surface-treated fillermaterial product comprising layer of the mono or multi-layer polyesterfilm comprises the thermoplastic polymer in an amount being below theamount of the surface-treated filler material product. For example, theat least one polyester and surface-treated filler material productcomprising layer of the mono or multi-layer polyester film comprises thethermoplastic polymer in an amount being at least 20 wt.-%, morepreferably at least 30 wt.-% and most preferably at least 50 wt.-%,based on the total weight of the surface-treated filler materialproduct, below the amount of the surface-treated filler materialproduct.

Additionally or alternatively, the at least one polyester andsurface-treated filler material product comprising layer of the filmfurther comprises an inorganic filler material different from thesurface-treated filler material product. Preferably, the inorganicfiller material different from the surface-treated filler materialproduct is selected from the group consisting of alumina, silica,titanium dioxide, alkaline metal salts, such as barium carbonate,calcium sulfate, barium sulfate and mixtures thereof. Barium sulfate isparticularly preferred as inorganic filler material.

It is appreciated that the presence of the inorganic filler materialdifferent from the surface-treated filler material product in the atleast one polyester and surface-treated filler material productcomprising layer of the mono or multi-layer polyester film isadvantageous as it acts as inorganic voiding agent and thus furtherimproves the formation of voids during the preparation of the film.Furthermore, the inorganic filler material different from thesurface-treated filler material product further increases the opaqueappearance of the film or layer.

However, if the at least one polyester and surface-treated fillermaterial product comprising layer of the film further comprises aninorganic filler material different from the surface-treated fillermaterial product, the amount of the inorganic filler material istypically below the amount of the surface-treated filler materialproduct.

For example, the at least one polyester and surface-treated fillermaterial product comprising layer of the film comprises the inorganicfiller material different from the surface-treated filler materialproduct in an amount of 1 to 10 wt.-%, based on the total weight of thelayer.

In one embodiment, the at least one polyester and surface-treated fillermaterial product comprising layer of the mono or multi-layer polyesterfilm comprises the inorganic filler material different from thesurface-treated filler material product in an amount being at least 20wt.-%, more preferably at least 30 wt.-% and most preferably at least 50wt.-%, based on the total weight of the surface-treated filler materialproduct, below the amount of the surface-treated filler materialproduct.

The weight median particle size d₅₀ of the inorganic filler materialdifferent from the surface-treated filler material product is preferablysimilar to the weight median particle size d₅₀ of the surface-treatedfiller material product. Thus, the inorganic filler material differentfrom the surface-treated filler material product preferably has a weightmedian particle size d₅₀ in the range from 0.5 μm to 3.0 μm, preferablyfrom 0.5 μm to 2.5 μm, more preferably from 0.5 μm to 2 μm, even morepreferably from 0.5 μm to 1.8 μm, and most preferably from 0.6 μm to 1.8μm.

Additionally or alternatively, the mono or multi-layer polyester filmmay additionally comprise additives which are typically used asadditives in the films to be produced. Advantageously, they are alreadyadded to the polymer or the polymer mixture prior to melting.Alternatively, said compounds can be added to the masterbatch.

For example, the mono or multi-layer polyester film comprises anadditive selected from the group consisting of light stabilizers,optical brightener, blue dyes, antiblocking agents, white pigments, andmixtures thereof.

Preferably, the at least one polyester and surface-treated fillermaterial product comprising layer comprises an additive selected fromthe group consisting of light stabilizers, optical brightener, bluedyes, antiblocking agents, white pigments, and mixtures thereof.

It is appreciated that light stabilizers which are UV stabilizers or UVabsorbers are chemical additives which can intervene in the physical andchemical processes of light-induced degradation. Carbon black and otherpigments can provide some degree of protection from the adverse effectsof light, but these substances are unsuitable for white films since theycause discoloration or color change. The only additives suitable forwhite films are organic or organometallic compounds which give no, oronly an extremely low level of, color or color change to the film to bestabilized. Light stabilizers which are suitable UV stabilizers absorbat least 70%, preferably 80%, particularly preferably 90%, of the UVlight in the wavelength range from 180 to 380 nm, preferably from 280 to350 nm. Those which are particularly suitable are those, which in thetemperature range from 260 to 300° C., are thermally stable, i.e. do notdecompose and do not cause release of gases. Examples of lightstabilizers which are suitable UV stabilizers are2-hydroxybenzophenones, 2-hydroxybenzotriazoles, organonickel compounds,salicylic esters, cinnamic ester derivatives, resorcinol monobenzoates,oxanilides, hydroxybenzoic esters, sterically hindered amines andtriazines, preferably 2-hydroxybenzotriazoles and triazines. Mostpreferably, the light stabilizer is hydroxy phenyl triazin(Tinuvin®1577, BASF, Ludwigshafen, Germany). The amounts of the lightstabilizers used are typically from 10 to 50 000 ppm, preferably from 20to 30 000 ppm, and most preferably from 50 to 25 000 ppm, based on thetotal weight of the film, preferably the at least one polyester andsurface-treated filler material product comprising layer.

A further additive present in the film, preferably the at least onepolyester and surface-treated filler material product comprising layer,if desired is an optical brightener. The optical brighteners accordingto the invention are capable of absorbing UV radiation in the wavelengthrange from about 360 to 380 nm and of emitting this again as visible,longer-wavelength, blue-violet light. Suitable optical brighteners arebisbenzoxazoles, phenylcoumarins and bissterylbiphenyls, in particularphenyl coumarin, and particularly preferably triazine-phenylcoumarin(Tinopal®, BASF, Ludwigshafen, Germany). The amounts of the opticalbrighteners used are typically from 10 to 50 000 ppm, preferably from 20to 30 000 ppm, and most preferably from 50 to 25 000 ppm, based on thetotal weight of the film, preferably the at least one polyester andsurface-treated filler material product comprising layer.

Suitable white pigments are preferably titanium dioxide, barium sulfate,calcium carbonate, kaolin and silica, and preference is given totitanium dioxide and barium sulfate. The titanium dioxide particles maybe composed of anatase or of brookite or of rutile, preferablypredominantly of rutile, which has higher hiding power than anatase. Ina preferred embodiment, 95 wt.-% of the titanium dioxide particles arerutile. The weight median particle size d₅₀ of the white pigment istypically below the weight median particle size d₅₀ of thesurface-treated filler material product and thus the white pigment doesnot act as a voiding agent. Preferable, the weight median particle sized₅₀ of the white pigment is in the range from 0.10 to 0.30 μm. Theamount of the white pigment in the film, preferably the at least onepolyester and surface-treated filler material product comprising layer,is usefully from 0.3 to 25 wt.-%, based on the total weight of the film,preferably the at least one polyester and surface-treated fillermaterial product comprising layer.

Additionally or alternatively, blue dyes, preferably blue dyes solublein polyester, may also be added to the film, preferably the at least onepolyester and surface-treated filler material product comprising layer,if this is useful. For example, blue dyes which have proven successfulare selected from cobalt blue, ultramarine blue and anthraquinone dyes,in particular Sudan blue 2 (BASF, Ludwigshafen, Germany). The amounts ofthe blue dyes used are typically from 10 to 10 000 ppm, preferably from20 to 5 000 ppm, and most preferably from 50 to 1 000 ppm, based on thetotal weight of the film, preferably the at least one polyester andsurface-treated filler material product comprising layer.

Additionally or alternatively, antiblocking agents may also be added tothe film, preferably the at least one polyester and surface-treatedfiller material product comprising layer, if this is useful. Typicalantiblocking agents are inorganic and/or organic particles, for examplecalcium carbonate different from the surface-treated filler materialproduct, amorphous silica, talcum, magnesium carbonate, bariumcarbonate, calcium sulfate, barium sulfate, lithium phosphate, calciumphosphate, magnesium phosphate, aluminum oxide, carbon black, titaniumdioxide, kaolin, or crosslinked polymer particles, for examplepolystyrene, acrylate, PMMA particles, or crosslinked silicones.Muscovite mica having an average particle size (weighted average) of 4.0to 12.0 μm, preferably 6.0 to 10.0 μm, is also particularly suitable. Asis generally known, mica is composed of platelet-like silicates, theaspect ratio of which is preferably in the range from 5.0 to 50.0.Mixtures of two and more different antiblocking agents or mixtures ofantiblocking agents having the same composition but a different particlesize can also be chosen as additives. The particles can be addeddirectly or by means of masterbatches to the polymers of the individuallayers of the film in the respective advantageous concentrations duringextrusion.

Antiblocking agents are preferably added to the outer layer(s), i.e. thelayer being free of the surface-treated filler material product. Theamounts of the antiblocking agent is generally from 0.01 to 1 wt.-%,based on the total weight of the film, preferably the at least onepolyester and surface-treated filler material product comprising layer.

It is appreciated that the compounds which are used as additives can bepresent in the at least one polyester and surface-treated fillermaterial product comprising layer. In case of a multi-layer film, thecompounds which are used as additives can be present in the at least onepolyester and surface-treated filler material product comprising layerand/or in at least one of the additional layer(s).

The mono or multi-layer polyester film of the present invention may beproduced by any method known in the art. According to one embodiment, aprocess of producing a mono or multi-layer polyester film comprises thesteps of:

-   -   a) providing a composition comprising at least one polyester and        a surface-treated filler material product, and    -   b) forming a film from the composition of step a), wherein the        surface-treated filler material product comprises    -   A) at least one ground calcium carbonate-comprising filler        material having a weight median particle size d₅₀ in the range        from 0.5 μm to 3.0 μm, and    -   B) a treatment layer on the surface of the at least one ground        calcium carbonate-comprising filler material comprising        -   i. a phosphoric acid ester blend of one or more phosphoric            acid mono-ester and salty reaction products thereof and/or            one or more phosphoric acid di-ester and salty reaction            products thereof, and/or        -   ii. at least one saturated aliphatic linear or branched            carboxylic acid and salty reaction products thereof, and/or        -   iii. at least one aliphatic aldehyde and/or salty reaction            products thereof, and/or        -   iv. at least one mono-substituted succinic anhydride            consisting of succinic anhydride mono-substituted with a            group selected from a linear, branched, aliphatic and cyclic            group having a total amount of carbon atoms from at least C₂            to C₃₀ in the substituent and/or salty reaction products            thereof, and/or        -   v. at least one polydialkylsiloxane, and/or        -   vi. mixtures of the materials according to i. to v.,    -   wherein the surface-treated filler material product comprises        the treatment layer in an amount of from 0.1 to 2.3 wt.-%, based        on the total dry weight of the at least one ground calcium        carbonate-comprising filler material.

The composition of the at least one polyester and the surface-treatedfiller material product provided in process step a) can be a masterbatchor compound obtained by mixing and/or kneading the at least onepolyester and the surface-treated filler material product to form amixture. The at least one polyester and the surface-treated fillermaterial product, and, if present, other optional additives, may bemixed and/or kneaded by the use of a suitable mixer, e.g. a Henschelmixer, a super mixer, a tumbler type mixer or the like. The compoundingstep may be done with a suitable extruder, preferably by a twin screwextruder (co or counter-rotating) or by any other suitable continuouscompounding equipment, e.g. a continuous co-kneader (Buss), a continuousmixer (Farrel Pomini), a ring extruder (Extricom) or the like. Thecontinuous polymer mass from extrusion may be either pelletized by (hotcut) die face pelletizing with underwater pelletizing, eccentricpelletizing and water ring pelletizing or by (cold cut) strandpelletizing with underwater and conventional strand pelletizing to formthe extruded polymer mass into pellets. Thus, the compound may be inform of pellets, beads, or granules.

Preferably, the composition of the at least one polyester and thesurface-treated filler material product provided in process step a) is amasterbatch or compound obtained by mixing and/or kneading the at leastone polyester and the surface-treated filler material product to form amixture and continuously pelletizing the obtained mixture. For example,the continuously pelletizing is carried out under water.

Optionally, the compounding step may also be performed with adiscontinuous or batch process using an internal (batch) mixer, e.g. aBanburry mixer (HF Mixing Group) or a Brabender mixer (Brabender) or thelike.

According to one embodiment the masterbatch or compound comprises thesurface-treated filler material product in an amount of from >30 wt.-%,preferably from >30 to 85.0 wt.-%, more preferably from 30.01 to 85.0wt.-%, even more preferably from 30.1 to 85.0 wt.-%, still morepreferably from 30.5 to 85.0 wt.-%, still even more preferably from 31.0to 85.0 wt.-%, and most preferably from 35.0 to 80.0 wt.-%, e.g. from 40to 70 wt.-%, based on the total weight of the masterbatch or compound.

It is appreciated that the composition provided in process step a) ispreferably prepared by using polyester flakes, such as PET flakes. Inthis regard, it is preferred that the polyester flakes, e.g. the PETflakes, are pre-dried before preparing the composition of step a) toremove the moisture. For example, the polyester flakes, such as PETflakes, are pre-dried at 90° C. for 6 hours.

According to an optional embodiment, the composition provided in processstep a) further comprises one or more of the additives/compoundsdescribed above.

The masterbatch or compound is preferably mixed with the same ordifferent polyester (as used as matrix in the masterbatch or compound)and/or one or more additives described above before process step b) iscarried out. According to a preferred embodiment, the masterbatch orcompound is mixed with the same polyester (as used as matrix in themasterbatch or compound) before process step b) is carried out.

In one embodiment, the additives which are typically used as additives,e.g. light stabilizers, optical brightener, blue dyes, antiblockingagents, white pigments, and mixtures thereof, are added to themasterbatch.

Alternatively, process steps a) and b) are carried out simultaneously.Preferably, process steps a) and b) are carried out simultaneously inthat the at least one polyester, more preferably pre-dried polyesterflakes, e.g. pre-dried PET flakes, and the surface-treated fillermaterial product, more preferably dry surface-treated filler materialproduct, are added directly into an extruder to carry out process stepb). That is to say, the composition of the at least one polyester andthe surface-treated filler material product provided in process step a)is obtained by directly adding the surface-treated filler materialproduct, preferably dry surface-treated filler material product, and theat least one polyester, more preferably pre-dried polyester flakes, e.g.pre-dried PET flakes, into the extruder to carry out process step b).

Alternatively, the composition comprising at least one polyester and asurface-treated filler material product of step a) is obtained by addingthe surface-treated filler material product to the polycondensationprocess of the at least one polyester. That is to say, the compositioncomprising at least one polyester and a surface-treated filler materialproduct of step a) is obtained by adding the surface-treated fillermaterial product either before or during or after to thepolycondensation process of the at least one polyester. For example, thecomposition comprising at least one polyester and a surface-treatedfiller material product of step a) is obtained by adding thesurface-treated filler material product either before or after,preferably after, to the polycondensation process of the at least onepolyester. Thus, the composition comprising at least one polyester and asurface-treated filler material product of step a) can be provided asready to use composition.

It is appreciated that materials such as the polyester-recyclingmaterial may already contain the surface-treated filler material productof the present invention. In this embodiment, the amount ofsurface-treated filler material product additionally added in processstep a) can thus be adapted accordingly to a lower amount in order toarrive at the desired content of the surface-treated filler materialproduct in the mono or multi-layer polyester film.

The process step b) may be carried out by any well-known techniques usedfor preparing polymer films. Examples of suitable film extrusiontechniques are blown film extrusion or cast film extrusion.

Accordingly, process step b) is preferably an extrusion process.

In a preferred extrusion process for forming the film, the meltedcomposition of the at least one polyester and the surface-treated fillermaterial product provided in process step a) is extruded through a slotdie and, in the form of a substantially amorphous prefilm, quenched on achill roll.

In one embodiment, the process further comprises a step c) of stretchingthe film obtained in step b) in only one direction among machinedirection (MD) or transverse direction (TD).

If a mono axially oriented film is prepared, the stretching of the filmobtained in step b) is carried out in machine direction (MD) ortransverse direction (TD), preferably in machine direction (MD).

The stretching step c) may be carried out by any means known in the art.Such methods and devices for performing stretching step c) are known inthe art, for example as LISIM known. LISIM procedures are described indetail in EP 1112167 and EP 0785858, which is herewith incorporated byreference.

During the stretching step, the polyester may be delaminated from thesurface of the surface-treated filler material product, whereby voidsare formed in the mono or multi-layer polyester film.

The stretching may be carried out by one step or by several steps.According to one embodiment process step c) is carried out from 1 to 10times.

Stretch magnification determines film breakage at high stretching aswell as breathability and the water vapor transmission of the obtainedfilm, and so excessively high stretch magnification and excessively lowstretch magnification are desirably avoided. According to oneembodiment, in process step c), the film obtained in step b) isstretched to a stretch magnification from 1.2 to 6 times, morepreferably 1.2 to 4 times into each direction.

Preferably, stretching step c) is carried out in that the film obtainedin step b) is stretched

-   -   a) in machine direction (MD) with a stretching ratio from 2 to        6, preferably from 3 to 4.5, or    -   b) in transverse direction (TD) with a stretching ratio from 2        to 5, preferably from 3 to 4.5.

According to one embodiment, process step c) is carried out at astretching temperature ranging from T_(g)+10° C. to T_(g)+60° C.(T_(g)=glass transition temperature).

The inventors of the present invention found that the mono ormulti-layer polyester film according to the present invention,especially the at least one polyester and surface-treated fillermaterial product comprising layer, has especially high filler content.Furthermore, the polyester film, especially the at least one polyesterand surface-treated filler material product comprising layer, is highlymicroporous at low density, especially the density is below the densitytypically achieved for films or layers using barium sulfate or titaniumdioxide as voiding agent. Furthermore, the polyester film, especiallythe at least one polyester and surface-treated filler material productcomprising layer, has an opaque appearance and can be prepared withoutfilm/layer breakage. Furthermore, the mono or multi-layer polyesterfilm, especially the at least one polyester and surface-treated fillermaterial product comprising layer, provides good mechanical propertiessuch as tensile strength, elongation at break or modulus of elasticityand optical properties such as gloss and transmittance.

The mono or multi-layer polyester film according to the presentinvention can be used in many different applications. According to oneembodiment, the mono or multi-layer polyester film is used in packagingproducts, preferably flexible packaging products, food contactapplications, paper or glass coverings, insulating materials, solar,preferably photovoltaic front or backsheets, marine or aviationapplications, science, electronic or acoustic applications, preferablydisplays, wires, cables, radio frequency identifications, flexiblecircuits, graphic arts, preferably labels, stone paper, preferably bags,packages, boxes, books, booklets, brochures, loyalty cards, businesscards, greeting cards, corrugated boards, envelopes, food trays,labelling, games, tags, magazines, signage, billboards, stationary,diaries, pads or notebooks, and holograms, filter products, cosmeticproducts, household products imaging, recording media, preferablyphotographic paper, X-ray film or thermal transfer imaging or industrialproducts, preferably capacitors, release sheets, fiberglass panels,laminating films, hot stamping foils or insulation facing.

According to a further aspect of the present invention, an articlecomprising the mono or multi-layer polyester film according to thepresent invention is provided, wherein the article is selected from thegroup consisting of packaging products, preferably flexible packagingproducts, food contact applications, paper or glass coverings,insulating materials, solar, preferably photovoltaic front orbacksheets, marine or aviation applications, science, electronic oracoustic applications, preferably displays, wires, cables, radiofrequency identifications, flexible circuits, graphic arts, preferablylabels, stone paper, preferably bags, packages, boxes, books, booklets,brochures, loyalty cards, business cards, greeting cards, corrugatedboards, envelopes, food trays, labelling, games, tags, magazines,signage, billboards, stationary, diaries, pads or notebooks, andholograms, filter products, cosmetic products, household productsimaging, recording media, preferably photographic paper, X-ray film orthermal transfer imaging or industrial products, preferably capacitors,release sheets, fiberglass panels, laminating films, hot stamping foilsor insulation facing.

The scope and interest of the invention will be better understood basedon the following examples which are intended to illustrate certainembodiments of the present invention and are non-limitative.

EXAMPLES 1 Measurement Methods and Materials

In the following, measurement methods and materials implemented in theexamples are described.

Intrinsic Viscosity

The intrinsic viscosity is measured according to DIN ISO 1628/1 and DINISO 1628/5, October 1999 (in decalin at 135° C.).

MFR₂

The MFR₂ is measured according to ISO 1133 (230° C., 2.16 kg load).

Crystallization Temperature T_(c)

The crystallization temperature is measured by differential scanningcalorimetry (DSC) on a Mettler-Toledo “Polymer DSC instrument(Mettler-Toledo (Schweiz) GmbH, Switzerland). The crystallization curvewas obtained during 10° C./min cooling and heating scans between 30° C.and 225° C. Crystallization temperatures were taken as the peak ofendotherms and exotherms.

Particle Size

The particle distribution of the untreated ground calciumcarbonate-comprising filler material was measured using a Sedigraph 5100from the company Micromeritics, USA. The method and the instruments areknown to the skilled person and are commonly used to determine grainsize of fillers and pigments. The measurement was carried out in anaqueous solution comprising 0.1 wt.-% Na₄P₂O₇. The samples weredispersed using a high speed stirrer and supersonics.

Specific Surface Area (BET)

Throughout the present document, the specific surface area (in m²/g) ofthe filler material is determined using the BET method (using nitrogenas adsorbing gas), which is well known to the skilled man (ISO9277:2010).

Ash Content

The ash content in [wt.-%] of the masterbatches and films was determinedby incineration of a sample in an incineration crucible which is putinto an incineration furnace at 570° C. for 2 hours. The ash content wasmeasured as the total amount of remaining inorganic residues.

Film Thickness

The film thickness was determined using a digital measuring slideMitutoyo IP 66 (Mitutoyo Europe GmbH, Neuss, Germany). Measured valueswere reported in μm.

Density of a Film or Layer

The density was determined from a test piece whereby a precise area offilm (100 mm×100 mm) is cut and weighed on an analytical balance. Anaverage film thickness was determined by taking nine thicknessmeasurements allocated over the whole film surface. The density wascalculated and reported in [g/cm³]. Also an average yield in m²/kg andthe unit weight in g/m² can be calculated from these values.

Moisture Pick-Up

The term “moisture pick-up susceptibility” in the meaning of the presentinvention refers to the amount of moisture absorbed on the surface ofthe filler and is determined in mg moisture/g of the dry treated mineralfiller product after exposure to an atmosphere of 10 and 85% of relativehumidity, resp., for 2.5 hours at a temperature of +23° C. (±2° C.). Thetreated mineral filler product is first held at an atmosphere of 10% ofrelative humidity for 2.5 hours then the atmosphere is changed to 85% ofrelative humidity, where the sample is held for another 2.5 hours. Theweight increase between 10% and 85% relative humidity is then used tocalculate the moisture pick-up in mg moisture/g of dry treated fillerproduct. The blank value of the equipment was determined as being 0.15to 0.2 mg/g, e.g. 0.19 mg/g. The results in the present application arenet values, i.e. the measured value minus the blank value.

Hydrophilicity

The “hydrophilicity” of a filler is evaluated at +23° C. by determiningthe minimum water to ethanol ratio in a volume/volume basedwater/ethanol-mixture needed for the settling of the majority of saidfiller, where said filler is deposited on the surface of saidwater/ethanol-mixture by passage through a house hold tea sieve. Thevolume/volume base is related to the volumes of both separate liquidsbefore blending them together and do not include the volume contractionof the blend. The evaluation at +23° C. refers to a temperature of +23°C.±2° C.

A 8:2 volumetric ratio of a water/ethanol-mixture has typically asurface tension of 41 mN/m and a 6:4 volumetric ratio of awater/ethanol-mixture has typically a surface tension of 26 mN/mmeasured at +23° C. (±2° C.) as described in the “Handbook of Chemistryand Physics”, 84^(th) edition, David R. Lide, 2003 (first edition 1913).

Measurement of the Total Volatiles

For the purpose of the present application, the “total volatiles”associated with fillers and evolved over a temperature range of 25 to350° C. is characterized according to % mass loss of the filler sampleover a temperature range as read on a thermogravimetric (TGA) curve.

TGA analytical methods provide information regarding losses of mass andvolatile onset temperatures with great accuracy, and is commonknowledge; it is, for example, described in “Principles of Instrumentalanalysis”, fifth edition, Skoog, Holler, Nieman, 1998 (first edition1992) in Chapter 31 pages 798 to 800, and in many other commonly knownreference works. In the present invention, thermogravimetric analysis(TGA) is performed using a Mettler Toledo TGA 851 based on a sample of500+/−50 mg and scanning temperatures from 25 to 350° C. at a rate of20° C./minute under an air flow of 70 ml/min.

The skilled man will be able to determine the “volatile onsettemperature” by analysis of the TGA curve as follows: the firstderivative of the TGA curve is obtained and the inflection pointsthereon between 150 and 350° C. are identified. Of the inflection pointshaving a tangential slope value of greater than 45° relative to ahorizontal line, the one having the lowest associated temperature above200° C. is identified. The temperature value associated with this lowesttemperature inflection point of the first derivative curve is the“volatile onset temperature”.

The “total volatiles” evolved on the TGA curve is determined using StareSW 9.01 software. Using this software, the curve is first normalisedrelative to the original sample weight in order to obtain mass losses in% values relative to the original sample. Thereafter, the temperaturerange of 25 to 350° C. is selected and the step horizontal (in German:“Stufe horizontal”) option selected in order to obtain the % mass lossover the selected temperature range.

Opacity

The opacity measurements were done according to DIN 53146 by measuringthe whiteness of a film sample on a black and a white substrate using aByk-Gardner Spectro-Guide (Byk-Gardner GmbH, Germany). The opacity isthe contrast ratio of the two measurements. The units are percent % anda perfectly opaque material will have an opacity value of 100%.

Water Vapor Transmission Rate (WVTR)

The WVTR value of the polyester films was measured with a Lyssy L80-5000(PBI-Dansensor A/S, Denmark) measuring device according to ASTM E398.

2 Materials

CC1 (inventive): Natural ground calcium carbonate, stone feedcommercially available from Omya International AG, Switzerland (d₅₀: 0.8μm; d₉₈: 3 μm, content of particles<0.5 μm=35%), surface-treated with1.7 wt.-% stearic acid (commercially available from Sigma-Aldrich,Croda) based on the total weight of the natural ground calciumcarbonate. BET: 8.5 m²/g.

CC2 (inventive): Natural ground calcium carbonate, stone feedcommercially available from Omya International AG, Switzerland (d₅₀: 0.8μm; d₉₈: 3 μm, content of particles<0.5 μm=35%), surface-treated with1.7 wt.-% alkenyl succinic anhydride (CAS [68784-12-3],concentration>93%) based on the total weight of the natural groundcalcium carbonate. BET: 8.5 m²/g.

CC3 (inventive): Natural ground calcium carbonate, stone feedcommercially available from Omya International AG, Switzerland (d₅₀: 1.7μm; d₉₈: 6 μm, content of particles<0.5 μm=12%), surface-treated with1.0 wt. % stearic acid (commercially available from Sigma-Aldrich,Croda) based on the total weight of the natural ground calciumcarbonate. BET: 3.4 m²/g.

CC4 (inventive): Natural ground calcium carbonate, stone feedcommercially available from Omya International AG, Switzerland (d₅₀: 1.7μm; d₉₈: 6 μm, content of particles <0.5 μm=12%), surface-treated with0.7 wt. % alkenyl succinic anhydride (CAS [68784-12-3],concentration>93%) based on the total weight of the natural groundcalcium carbonate. BET: 3.4 m²/g.

CC5 (inventive): Natural ground calcium carbonate, stone feedcommercially available from Omya International AG, Switzerland (d₅₀: 1.7μm; d₉₈: 6.5 μm, content of particles<2 μm=57%), surface-treated with 1wt.-% stearic acid (commercially available from Sigma-Aldrich, Croda)based on the total weight of the natural ground calcium carbonate. BET:4 m²/g.

CC6 (inventive): Natural ground calcium carbonate, stone feedcommercially available from Omya International AG, Switzerland (d₅₀: 2.6μm; d₉₈: 15 μm, content of particles<2 μm=38%), surface-treated with 0.6wt.-% stearic acid (commercially available from Sigma-Aldrich, Croda)based on the total weight of the natural ground calcium carbonate. BET:2.5 m²/g.

CC7 (comparative): Natural ground calcium carbonate, commerciallyavailable from Omya International AG, Switzerland (d₅₀: 5 μm; d₉₈: 20μm), surface-treated with 0.5 wt.-% stearic acid (commercially availablefrom Sigma-Aldrich, Croda) based on the total weight of the naturalground calcium carbonate. BET: 2.1 m²/g.

CC8 (comparative): Natural ground calcium carbonate, commerciallyavailable from Omya International AG, Switzerland (d₅₀: 5 μm; d₉₈: 30μm), without surface-treatment. BET: 2.1 m²/g.

The surface-treatment of CC1 to CC7 has been carried out by using themethods described in EP 2 722 368 A1.

P1: Polyethylene terephthalate (PET), Lighter C93 PET, commerciallyavailable from Equipolymers GmbH, Germany (intrinsic viscosity: 0.8±0.02dl/g, crystallinity min. 50%, melting point 247° C., according to thetechnical data sheet provided by the supplier).

3 Examples Example 1—Preparation of Masterbatches

Polypropylene masterbatches containing the calcium carbonate fillers CC1to CC8 and the polymer P1 were continuously prepared on a lab scale Busskneader (Buss PR46 from Buss AG, Switzerland). The polymer P1 waspre-dried prior to processing in an oven at 160° C. for 4 hours. Thecompositions and filler contents of the prepared masterbatches arecompiled in Table 1 below. The precise filler content was determined bythe ash content.

TABLE 1 Composition and filler content of prepared masterbatches. Fillercontent Masterbatch Filler [wt.-%] MB1 (inventive) CC1 50 MB2(inventive) CC2 50 MB3 (inventive) CC3 50 MB4 (inventive) CC4 50 MB5(inventive) CC5 50 MB6 (inventive) CC6 50 MB7 (comparative) CC7 50 MB8(comparative) CC8 50

Masterbatches MB1 to MB6 could be produced in good quality, whereasmasterbatches MB7 and MB8 were difficult to compound and receivedpellets were of bad quality.

Example 2—Preparation of Polyester Cast Films Via Masterbatch

Cast films were prepared on a Collin Laboratory Film Line (Dr. CollinGmbH, Germany) with a twin screw extruder with a diameter of 30 mm wideT-die and a take-up system, which had temperature controlledchill-rolls. The chilled roll was kept 20 mm from the T-die to produce apolyester sheet having a thickness of around 1 000 μm. The extruder anddie temperatures were consistent throughout the experiment. The dietemperature was set at 270° C.; the line speed was 0.5 m/min. Themasterbatch or polymer was mixed with the neat polymer P1 to receivecast films with the concentrations given in Table 2.

TABLE 2 Compositions and properties of prepared cast films Fillercontent Film Sample Masterbatch [wt.-%]  1 (comp.) no 0  2 (inv.) MB1 35 3 (inv.) MB1 45  4 (inv.) MB2 35  5 (inv.) MB2 45  6 (inv.) MB3 35  7(inv.) MB3 45  8 (inv.) MB4 35  9 (inv.) MB4 45 10 (inv.) MB5 35 11(inv.) MB5 45 12 (inv.) MB6 35 13 (inv.) MB6 45

All films shown in Table 2 are cast films which were produced in goodquality with visual good appearance.

Example 3—Preparation of Polyester Cast Films Via Direct Extrusion

Cast films were prepared on a Collin Laboratory Film Line (Dr. CollinGmbH, Germany) with a twin screw extruder with a diameter of 30 mm wideT-die and a take-up system, which had temperature controlledchill-rolls. The chilled roll was kept 20 mm from the T-die to produce apolypropylene sheet having a thickness of around 1 000 μm. The extruderis equipped with a vacuum venting system to remove during the extrusionvolatiles and moisture coming from the raw materials. The extruder anddie temperatures were consistent throughout the experiment. The dietemperature was set at 270° C.; the line speed was 0.5 m/min. Themasterbatch or polymer was mixed with the neat polymer P1 to receivecast films with the concentrations given in Table 2.

TABLE 3 Compositions and properties of prepared cast films Fillercontent Film Sample Filler [wt.-%]  1 (comp.) no 0  2 (inv.) CC1 60  3(inv.) CC1 70  4 (inv.) CC2 60  5 (inv.) CC2 70  6 (inv.) CC3 60  7(inv.) CC3 70  8 (inv.) CC4 60  9 (inv.) CC4 70 10 (inv.) CC5 60 11(inv.) CC5 70 12 (inv.) CC6 60 13 (inv.) CC6 70

1. A mono or multi-layer polyester film, wherein at least one layer ofthe film comprises at least one polyester in an amount ranging from 20.0wt.-% to <70 wt.-% and a surface-treated filler material product in anamount ranging from >30 wt.-% to 80.0 wt.-%, based on the total weightof the layer, wherein the surface-treated filler material productcomprises A) at least one ground calcium carbonate-comprising fillermaterial having a weight median particle size d₅₀ in the range from 0.5μm to 3.0 μm, and B) a treatment layer on the surface of the at leastone ground calcium carbonate-comprising filler material comprising i. aphosphoric acid ester blend of one or more phosphoric acid mono-esterand salty reaction products thereof and/or one or more phosphoric aciddi-ester and salty reaction products thereof, and/or ii. at least onesaturated aliphatic linear or branched carboxylic acid and a saltyreaction product thereof, and/or iii. at least one aliphatic aldehydeand/or a salty reaction product thereof, and/or iv. at least onemono-substituted succinic anhydride comprising a succinic anhydridemono-substituted with a group that is a linear, branched, aliphatic orcyclic group having a total number of carbon atoms from at least C₂ toC₃₀ in the substituent and/or a salty reaction product thereof, and/orv. at least one polydialkylsiloxane, and/or vi. mixtures of thematerials according to i. to v., wherein the surface-treated fillermaterial product comprises the treatment layer in an amount of from 0.1wt.-% to 2.3 wt.-%, based on the total dry weight of the at least oneground calcium carbonate-comprising filler material.
 2. The mono ormulti-layer polyester film of claim 1, wherein the at least onepolyester and surface-treated filler material product comprising layerof the film comprises the surface-treated filler material product in anamount ranging from 30.01 wt.-% to 80.0 wt.-%, based on the total weightof the layer.
 3. The mono or multi-layer polyester film of claim 1,wherein the at least one polyester is selected from the group consistingof polyglycolic acid (PGA), polylactic acid (PLA), polycaprolactone(PCL), polyhydroxybutyrate (PHB), polyethylene terephthalate (PET),polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT),polyethylene naphthalate (PEN), polyethylene furanoate (PEF), bio-basedpolyesters, polyester-recycling materials and mixtures thereof.
 4. Themono or multi-layer polyester film of-claim 1, wherein the at least onepolyester and surface-treated filler material product comprising layerof the film comprises the at least one polyester in an amount rangingfrom 20.0 wt.-% to 69.99 wt.-%, based on the total weight of the layer.5. The mono or multi-layer polyester film of-claim 1, wherein the atleast one ground calcium carbonate-comprising filler material is a wetor dry ground calcium carbonate-comprising filler material andoptionally is a wet ground calcium carbonate-comprising filler.
 6. Themono or multi-layer polyester film of-claim 1, wherein the at least oneground calcium carbonate-comprising filler material is natural groundcalcium carbonate, precipitated calcium carbonate, modified calciumcarbonate, surface-treated calcium carbonate, or a mixture thereof. 7.The mono or multi-layer polyester film of-claim 1, wherein the at leastone ground calcium carbonate-comprising filler material has a) a weightmedian particle size d₅₀ from 0.5 μm to 2.5 μm, and/or b) a top cutparticle size d₉₈ of 15 μm, and/or c) a fineness such that at least 15wt.-%, of all particles have a particle size of <0.5 μm, and/or d) aspecific surface area (BET) of from 0.5 m²/g to 150 m²/g, as measuredusing nitrogen and the BET method according to ISO
 9277. 8. The mono ormulti-layer polyester film of-claim 1, wherein the treatment layer onthe surface of the at least one ground calcium carbonate-comprisingfiller material comprises at least one saturated aliphatic linear orbranched carboxylic acid and salty reaction products thereof.
 9. Themono or multi-layer polyester film of-claim 1, wherein thesurface-treated filler material product comprises the treatment layer inan amount selected from the group consisting of from 0.2 wt.-% to 2.0wt.-%, from 0.4 wt.-% to 1.9 wt.-%, and from 0.5 wt.-% to 1.8 wt.-%,based on the total dry weight of the at least one ground calciumcarbonate-comprising filler material.
 10. The mono or multi-layerpolyester film of-claim 1, wherein the at least one polyester andsurface-treated filler material product comprising layer of the filmfurther comprises a thermoplastic polymer, optionally crosslinked with acrosslinking agent, wherein the thermoplastic polymer is selected fromthe group consisting of a polyolefin selected from the group consistingof polypropylene, polyethylene, polybutylene, and mixtures thereof, acyclic olefin copolymer (COC), a polyketone, a polysulphone, afluoropolymer, a polyacetal, an ionomer, an acrylic resin, a polystyreneresin, a polyurethane, a polyamide, a polycarbonate, a polyacrylonitrileand a copolymerized resin and mixtures thereof, which is dispersed inthe at least one polyester.
 11. The mono or multi-layer polyester filmof claim 10, wherein the at least one polyester and surface-treatedfiller material product comprising layer of the film comprises thethermoplastic polymer in a range selected from the group consisting offrom 0.1 wt.-% to 29.9 wt.-%, from 1 wt.-% to 28 wt.-%, from 2 wt.-% to26 wt.-%, from 3 wt.-% to 25 wt.-%, from 4.5 wt.-% to 23 wt.-%, and from4 wt.-% to 20 wt.-%, based on the total weight of the layer.
 12. Themono or multi-layer polyester film of claim 1, wherein the film,optionally the at least one polyester and surface-treated fillermaterial product comprising layer, has a) a density in a range selectedfrom the group consisting of from 1.8 g/cm³ to 2.4 g/cm³, from 1.8 g/cm³to 2.35 g/cm³, from 1.85 g/cm³ to 2.3 g/cm³ and from 1.9 g/cm³ to 2.25g/cm³, and/or b) an opacity selected from the group consisting of 50%,55% and 60%.
 13. The mono or multi-layer polyester film of-claim 1,wherein the at least one polyester and surface-treated filler materialproduct comprising layer of the film further comprises an inorganicfiller material different from the surface-treated filler materialproduct and optionally selected from the group consisting of alumina,silica, titanium dioxide, alkaline metal salts, including bariumcarbonate, calcium sulfate, barium sulfate and mixtures thereof,optionally in an amount of 1 wt.-% to 10 wt.-% based on the total weightof the layer.
 14. The mono or multi-layer polyester film of-claim 1,wherein the film, optionally the at least one polyester andsurface-treated filler material product comprising layer, comprises anadditive selected from the group consisting of light stabilizers,optionally 2-hydroxybenzophenones, 2-hydroxybenzotriazoles, organonickelcompounds, salicylic esters, cinnamic ester derivatives, resorcinolmonobenzoates, oxanilides, hydroxybenzoic esters, sterically hinderedamines and triazines, hydroxy-phenyl-triazin, optical brightener, bluedyes, blue dyes soluble in polyester, antiblocking agents, whitepigments and mixtures thereof.
 15. The mono or multi-layer polyesterfilm of-claim 1, wherein the film is a cast film, a blown film, a doublebubble film or a mono axially oriented polyester film.
 16. A process forproducing the mono or multi-layer polyester film as defined in-claim 1,the process comprising the steps of: a) providing a compositioncomprising at least one polyester and a surface-treated filler materialproduct, and b) forming a film from the composition of step a), whereinthe surface-treated filler material product comprises A) at least oneground calcium carbonate-comprising filler material having a weightmedian particle size d₅₀ in the range from 0.5 μm to 3.0 μm, and B) atreatment layer on the surface of the at least one ground calciumcarbonate-comprising filler material comprising i. a phosphoric acidester blend of one or more phosphoric acid mono-ester and a saltyreaction product thereof and/or one or more phosphoric acid di-ester anda salty reaction product thereof, and/or ii. at least one saturatedaliphatic linear or branched carboxylic acid and a salty reactionproduct thereof, and/or iii. at least one aliphatic aldehyde and/or asalty reaction product thereof, and/or iv. at least one mono-substitutedsuccinic anhydride consisting of succinic anhydride mono-substitutedwith a group—that is a linear, branched, aliphatic or cyclic grouphaving a total number of carbon atoms from at least C₂ to C₃₀ in thesubstituent and/or salty reaction product thereof, and/or v. at leastone polydialkylsiloxane, and/or vi. mixtures of the materials accordingto i. to v., wherein the surface-treated filler material productcomprises the treatment layer in an amount of from 0.1 wt.-% to 2.3wt.-%, based on the total dry weight of the at least one ground calciumcarbonate-comprising filler material.
 17. The process of claim 16,wherein the composition provided in step a) is a masterbatch obtained bymixing and/or kneading the at least one polyester and thesurface-treated filler material product to form a mixture andcontinuously pelletizing the obtained mixture or a compound obtained bymixing and/or kneading the at least one polyester and thesurface-treated filler material product to form a mixture andcontinuously pelletizing the obtained mixture.
 18. The process of claim16, wherein the composition provided in step a) is a masterbatch orcompound comprising the surface-treated filler material product in anamount selected from the group consisting of from >30 wt.-% to 85 wt.-%,from 35 wt.-% to 80 wt.-% and from 40 wt.-% to 70 wt.-%, based on thetotal weight of the masterbatch or compound.
 19. The process of claim16, wherein the composition comprising at least one polyester and asurface-treated filler material product of step a) is obtained by addingthe surface-treated filler material product, optionally before or after,to the polycondensation process of the at least one polyester.
 20. Theprocess of claim 16, wherein process steps a) and b) are carried outsimultaneously, optionally in that the at least one polyester and thesurface-treated filler material product are added directly into anextruder to carry out step b).
 21. The process of claim 16, wherein theprocess further comprises a step c) of stretching the film obtained instep b) in only one direction among machine direction (MD) or transversedirection (TD).
 22. A voiding agent in a mono or a multi-layer polyesterfilm, the voiding agent comprising a surface-treated filler materialproduct, wherein the polyester film is a mono or multi-layer polyesterfilm comprising at least one layer comprising at least one polyester inan amount ranging from 20.0 wt.-% to <70 wt.-% and the surface-treatedfiller material product in an amount ranging from >30 wt.-% to 80.0wt.-%, based on the total weight of the layer, wherein thesurface-treated filler material product comprises A) at least one groundcalcium carbonate-comprising filler material having a weight medianparticle size d₅₀ in the range from 0.5 μm to 3.0 μm, and B) a treatmentlayer on the surface of the at least one ground calciumcarbonate-comprising filler material comprising i. a phosphoric acidester blend of one or more phosphoric acid mono-ester and a saltyreaction product thereof and/or one or more phosphoric acid di-ester anda salty reaction product thereof, and/or ii. at least one saturatedaliphatic linear or branched carboxylic acid and a salty reactionproduct thereof, and/or iii. at least one aliphatic aldehyde and/or asalty reaction product thereof, and/or iv. at least one mono-substitutedsuccinic anhydride consisting of succinic anhydride mono-substitutedwith a group—that is a linear, branched, aliphatic or cyclic grouphaving a total number of carbon atoms from at least C₂ to C₃₀ in thesubstituent and/or a salty reaction product thereof, and/or v. at leastone polydialkylsiloxane, and/or vi. mixtures of the materials accordingto i. to v., wherein the surface-treated filler material productcomprises the treatment layer in an amount of from 0.1 wt.-% to 2.3wt.-%, based on the total dry weight of the at least one ground calciumcarbonate-comprising filler material.
 23. An article comprising a monoor multi-layer polyester film according to claim 1, wherein the articleis selected from the group consisting of packaging products, optionallyflexible packaging products, food contact applications, paper or glasscoverings, insulating materials, solar, optionally photovoltaic front orbacksheets, marine or aviation applications, science, electronic oracoustic applications, optionally displays, wires, cables, radiofrequency identifications, flexible circuits, graphic arts, preferablylabels, stone paper, optionally bags, packages, boxes, books, booklets,brochures, loyalty cards, business cards, greeting cards, corrugatedboards, envelopes, food trays, labelling, games, tags, magazines,signage, billboards, stationary, diaries, pads or notebooks, andholograms, filter products, cosmetic products, household productsimaging, recording media, optionally photographic paper, X-ray film orthermal transfer imaging or industrial products, optionally capacitors,release sheets, fiberglass panels, laminating films, hot stamping foilsand insulation facing.
 24. A method of making an article, the methodcomprising incorporating the mono or multi-layer polyester filmaccording to claim 1 into the article wherein the article is a packagingproduct, optionally a flexible packaging product, a food contactapplication, a paper or glass covering, an insulating material, solar,optionally photovoltaic front or backsheet, a marine or aviationapplication, a science, electronic or acoustic application, optionallydisplay, wire, cable, radio frequency identification, flexible circuit,graphic art, optionally label, stone paper, optionally bag, package,box, book, booklet, brochure, loyalty card, business card, greetingcard, corrugated board, envelope, food tray, labelling, game, tag,magazine, signage, billboard, stationary, diary, pad or notebook, andhologram, filter-product, cosmetic product, household product imaging,recording media, optionally photographic paper, X-ray film or thermaltransfer imaging or industrial product, optionally capacitor, releasesheet, fiberglass panel, laminating film, hot stamping foil orinsulation facing.
 25. The mono or multi-layer polyester film of claim8, wherein the at least one saturated aliphatic linear or branchedcarboxylic acid is selected from the group consisting of carboxylicacids consisting of pentanoic acid, hexanoic acid, heptanoic acid,octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, lauricacid, tridecanoic acid, myristic acid, pentadecanoic acid, palmiticacid, heptadecanoic acid, stearic acid, nonadecanoic acid, arachidicacid, heneicosylic acid, behenic acid, tricosylic acid, lignoceric acidand mixtures thereof, and/or at least one mono-substituted succinicanhydride consisting of succinic anhydride mono-substituted with a groupselected from a linear, branched, aliphatic and cyclic group having atotal amount of carbon atoms from at least C₂ to C₃₀ in the substituentand/or salty reaction products thereof.